Thomas E. Jeffrey Lisa Gitelman Gregory Jankunis David W. Hutchings Leslie Fields

Robert Rosenberg Director and Editor

Theresa M. Collins Gregory Field Aldo E. Salerno Karen A. Detig Lorie Stock


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University Publications of America Bethesda, MD 1999

Edison signature used with permission ofMcGraw-Edis

Thomas A. Edison Papers


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National Historical Publications and Records Commission 18 June 1981

Copyright © 1999 by Rutgers, The. State University

All rights reserved. No part of this publication including any portion of the guide and hidex or of the microfilm may be reproduced, stored hi a retrieval system, or transmitted hi any form by any means— graphic, electronic, mechanical, or chemical, hicludhigphotocopying, recordhigor taphig, or information storage and retrieval systems— witiiout written permission of Rutgers, The State University, New Brunswick, New Jersey.

The original documents hi this edition are from the archives at the Edison National Historic Site at West Orange, New Jersey.

ISBN 0-89093-703-6


Robert A. Rosenberg Director and Editor

Thomas E. Jeffrey Associate Director and Coeditor

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Managing Editor, Book Edition Helen Endick

Assistant Director for Admimstration

Associate Editors Theresa M. Collins Lisa Gitelman Keith A. Nier

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A Note on the Sources

The pages which have been filmed are the best copies available. Every technical effort possible has been made to ensure legibility.


Reel duplication of the whole or of any part of this film is prohibited. In lieu of transcripts, however, enlarged photocopies of selected items contained on these reels

may be made in order to facilitate research.


This material consists of correspondence, court records, and other items relating to patent interference proceedings and infringement suits and to other legal actions involving the technical development and commercial exploitation of Edison's cement machinery. Included are documents pertaining to Edison's crushing rolls, which were used in both iron ore processing and cement manufacture, and to his invention of a long rotary kiln for making cement.

Less than 10 percent of the documents have been selected. The selected items reflect Edison's personal involvement in legal matters, detail experimental work by Edison or his assistants, or broadly pertain to matters of corporate organization and patent management. Related material can be found in the records of the Edison Portland Cement Co. and the Edison Ore Milling Syndicate, Ltd. (Company Records Series). The documents are arranged in the following order:

Correspondence Interference Proceeding

Shiner v. Edison (No. 27,406)

Case File

Thomas A. Edison and the North American Portland Cement Company v. Aisen's American Portland Cement Works


This folder contains correspondence and other documents concerning a variety of legal matters. The selected documents cover the period 1902-1910. Among the correspondents are Edison; Frank L. Dyer of the Legal Department; Walter S. Mallory, vice president of the Edison Portland Cement Co.; and Edward Dinan, chemist. Included are letters pertaining to the technical development and operation of Edison's long kilns; to cement-related patents assigned to the Edison Ore Milling Syndicate, Ltd.; and to a proposed infringement suit against the Atlas Portland Cement Co. Also included is correspondence relating to the progress of litigation against the Allis- Chalmers Co. and to a possible deposition by Edison regarding the use of pulverized coal in cement kilns.

Interference Proceeding Shiner v. Edison (No. 27,406)

This folder contains material pertaining to a Patent Office proceeding involving an application filed by Edison on January 27, 1906, for a patent on a rotary kiln that he had invented in 1 899 and a competing application by William C. Shiner. The one selected item is Edison's brief on appeal to the commissioner of patents, who ruled in favor of Edison in June 1909.

Case File

Thomas A. Edison and the North American Portland Cement Company v.

Alsen's American Portland Cement Works

This folder contains material pertaining to the infringement suit brought by Edison and the North American Portland Cement Co. against Alsen's American Cement Works in the U.S. District Court for the Southern District of New York. The case was initiated in March 1908 and involved Edison's U.S. Patent 802,631 on long kilns. The court decided against Edison and declared his patent invalid on May 7, 1913. The selected items are from Complainants' Record on Final Hearing and Complainants' Brief on Final Hearing

Legal Department Records Cement - Correspondence

This folder contains correspondence and other documents concerning a variety of legal matters. The selected documents cover the period 1902- 1910. Among the correspondents are Edison; Frank L. Dyer of the Legal Department; Walters. Mallory, vice president of the Edison Portland Cement Co.; and Edward Dinan, chemist. Included are letters pertaining to the technical development and operation of Edison's long kilns; to cement- related patents assigned to the Edison Ore Milling Syndicate, Ltd.; and to a proposed infringement suit against the Atlas Portland Cement Co. Also included is correspondence relating to the progress of litigation against the Allis-Chalmers Co. and to a possible deposition by Edison regarding the use of pulverized coal in cement kilns.

Less than 10 percent of the documents have been selected. Among the items not selected are letters, memoranda, and reports regarding patent research; printed patents; a draft complaint and affadavit for use in the proposed case against the Atlas company; letters of transmittal and acknowledgment; registered mail receipts; and documents that duplicate the information in selected material.

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y/w July 7, 1902.

W. S. Mallory, Eb<i. ,

Edison laboratory,

Orange, K.

Dear Mr. Mallory, -

I enclose a copy of a letter dated the 25th ult. just received from the Edison Ore-Milling Syndicate and replying to our letter of the 11th ult. regarding the re¬ assignment of cement patents. I also enclose a copy of the letter from Mr. Lawrence to Mr. Edison referred to in the Syndicate letter. //






Copy of letter and enclosure

from Edison Ore-Milling Syndicate limited

to Dyer, Edmonds & Dyer.

London, W.C. , June 25th 1902.

Messrs. Dyer, Edmonds & Dyer,

31 Nassau Street,

New York.

Dear Sirs,

We are in receipt of your letter of the 11th inst. , asking us to arrange for the reassignment of certain patents, which Mr. Edison has already communicated to us, for the rea¬ son that they relate exclusively to the manufacture of cement.

This matter has been duly considered hy the Board of Directors, and we desire to point out that this subject wa3 discussed as far back as July 1900, when Mr. Edison raised the question whether one particular patent should have been communicated to us.

Mr. Lawrence, the Chairman of this Syndicate, imme¬ diately wrote a long letter to Mr. Edison (copy enclosed) pointing out that it had always been completely understood from Mr. Edison's letters and speeches that this Syndicate was to have the benefit of cement patents and in 1900 Mr. Dick, with Mr. Edison's concurrence and sanction, on behalf of this Syndicate, entered into negotiations in England for the sale of these patents to an important cement combine.


There are additional circumstances besides those men¬ tioned in Mr. Lawrence's letter which undoubtedly indicate Mr . Edison's intention to hand over cement patents to this Syndicate, in which he himself is so largely interested.

V/e venture to think therefore that there may be some misunderstanding on your part as to Mr. Edison's wishes in this matter, and we should be much obliged if you would fur¬ ther communicate with him, and in particular draw his atten¬ tion to Mr. Joseph Lawrence's letter to him of the 2nd August 1900, to which we may say that Mr. Edison did not make any reply.

Yours faithfully,


J. Hall Jnr.





July 19,1900.

Mr. I. Hall, Jr. ,

Seo. Edison Ore Milling Syndicate , Ltd. ,

7 Amberley House, Norfolk Street,

London, W. C. , England.

Dear Sir:-

In reply to your favor of the 6th ult., I heg to state that the patent you speak of was a cement patent, and does not come under the terms of the original contract. All patents coming under the oontraot will be communicated direct to the Syndicate, as has been the case heretofore, those relating to Cement Improvements, whloh owing to their character may not come under the oontraot I will take out direct.

You will be glad to know that the Mills at Edison, N.J. are running regularly except the Bricking plant. Owing to the reoent panic in Iron, the furnaces were overloaded with ore when we started up, so we will not ship briquettes until their surplus ore has been worked down to permit of their reoeiving briquettes.

We are turning out about 300 tons of Concentrate daily and stocking it.

As to the costs of concentrating, we are keeping accounts and hope to give you the results in a couple of months. We are not losing any money even with our 17 per cent crude ore, but how much we are making is an unknown quantity. The Zinc Mill continues to run regularly.

We are progressing rapidly with the Cement Mill.

Yours truly,

Thomas A. Edison,



Copy of letter from Mr. Joseph Lawrence to Mr. Thomas A. Edison.

2nd. August 1900.

My dear Edison,

The Secretary of the Edison Syndicate has shown me your letter of the 19th. July in reference to the specifica¬ tion Ho. 3485 of 1900, described as "method of and apparatus for grinding screening and rescreening very fine materials in bulk".

In your letter which although dated the 19th. July, did not reach us until the 31st. (evidently having missed two or three mails), you say this specification "does not come under the terms of the original contract."

The specification is not alone confined to cement, but applies also to iron, the terms being as follows

(A) "An invention relating to an improved method "and apparatus for grinding and screening very fine materials "in bulk such as iron ore, Portland Cement &c. , and to an "improved method of and apparatus for grinding In bulk the "ground and screened material. "

Under these circumstances, I have no doubt that you will see that the Syndicate is entitled to the benefit of this improvement under the terms of the original contract, indeed your patent attorneys, Messrs. Dyer admit as much in their letter to us of the 12th. July, wherein they stato they have v/ritten to their agents, Messrs. Brandon Bros, in Paris,, to look to our agent Mr. Woodroffe as their principal and to


take all instructions from him.

You will remember that in all your previous corres¬ pondence and especially in your speech to the shareholders in December last, you admit that the cement rights are 11 con¬ trolled by the Syndicate. " In your speech, after dealing with the cement works and the plant that was being erected, and the improvements that were being made in the same, you go on to urge the shareholders not to part "with any rights "for any purpose whatsoever until these two (cement) mills "have demonstrated commercially the valuable rights controlled "by the Syndicate. " You also go on to say that the "experi- "ments are being paid for from this side, the Syndicate "realizing without expense."

All these circumstances prove, without falling back on the terms of the Contract, that you regard the Syndicate as controlling all the cement rights, which naturally include the Improvements. In the Director's printed report (which was approved by Mr. Dick) which was sent out prior to the meeting, we speak, on the strength of your previous promise, of your communicating to us without cost certain improvements which relate to cement, and also state that "other valuable improvements will, it is promised also be communicated in a similar wayl' We have also, quite recently received four other specifications of new inventions one of which particu¬ larly relates to cement, and we have filed applications in

various countries in respect of them to protect the Syndi- cat e ' s rights .

Yours faithfully,

(Signed.) J. DAv/KJiiiJGE .


Dyer, Edmonds & Dyer,

31 Nassau Street,

Now York.

Dear Sirs:

X have yours of the 7th Inst, enclosing copy of letter of June 25th, 1902, from the Edison Ore Milling Syndicate (Limited, also copy of letter of August 2nd, 1900, from Mr. Joseph Lawrence, all of which have been oarefully noted.

There is no question but what the Syndicate are entitled to the Cement rights on all machinery which comeB in under the contract, but the machinery and devices designed specially for Cement work and invented after the oontract was made, doaB not go to them without further consideration to me. ^

The patents oovared by yours of June 11th, 1902, were assigned in error and should be re-assigned to me.

Yours very truly,

ZfinutA/: '^"Z'jMzU:

** " ' JAS^„,,^A

Sept. 22, 1902.

Thomaa A. Edison, Esq.,

Orange,^ I

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Dear Sir, U) »-C£ (Q-c,c tllU f-D U3s^L. <PW- &-t-s A C-

We have received from Edison Ore Milling Syndicate }\

limited a letter, dated 11th inst., as follows:

"Referring to the question of the assignment of oertain cement patents hy Mr. Edison to the Syndicate, it haB been arranged that the consideration of the mat¬ ter should he postponed until Mr. Dick is next in England, when a settlement satisfactory to all parties can no doubt ho arranged. 11

We assume that this means that an arrangement has heen made

directly with you to this effect.

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Mr T. A. Edison;


New Jersey',

U. 3. A.

Dear ;Sir,-'

At a Board Meeting of the Syndicate held on the 20th inst, , the discussion regarding certain of your cement patents, which had Been adjourned from the meeting held on the 10th' .September pending Mr Dick's return to England',, was resumed.

Mr Dick fully explained your views with regard- to the cement patents which have been communicated to Us by Messrs Dyer, Edmonds & Dyer and the feeling was at once expressed by "all the Direc¬ tors that there was no wish whatever on our part to ask you to give- us any patent rights to which we are not entitled,;- and which might be considered not to; be covered" by the scope of the original- agree¬ ment, with the Syndicate.

We do not in any way desire to take advantage of the fact that these cement patents have been communicated to us and that we

have filed patent, applications on them here and abroad.

In order to recognise the principle of the ownership of _ the patents the Directors have resolved to' offe'r you a percentage of profits in respect of any patent improvements invented by you oeing used hereafter, such improvements not being covered' by the original contract, and Mr Dick has been asked to consult with yoU on the matter upon his return to the United States.

We trust that you may consider this suggestion a fair ^one and that it may meet your wishes', but the Directors are arutioua. that it should not be felt for ohe moment that there is any" desire on their part to ask for more patent rights than they are entitled to), or Which you may feel willing to place' at their disposal in the interests of ail concerned.

Yours faithfully,


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Roaster Plant:

Mr. W. H. Ma&on, Supt.,

Edison Portland Cement Co., Stewartsville, N. J.

Dear Sir:-

Dec. 4, 1903

In reviewing the work of the kilns for some time past, it is evident that the speed of rotation of No.l kiln at least, should he lessened; and also that provision he made for changing the speed as desired with or without interfering with the speed of the chalk feed screw.

The main object we wish to aooomplish is good clink¬ er and more of it. The chief fault of the olinker bo far haB heen insufficient oxidation. The heat, as a rule, has heen sufficient, hut incomplete oxidation has heen repeatedly noticed and latterly it is more evident, since we have heen increasing the output.

Before taking up the case of our kilns, there are to he understood a few general points relative to the reparation of a 'kiln.

Elrst : The speed of the chalk feed sorew determines the

quantity of intake of chalk, and, consequently, the quantity of output of clinker. This is axiomatic, the more chalk you feed to a kiln, the more clinker/you will get.

Second: The speed of rotation of the kiln determines the

length of time required for a given quantity of chalk to come for¬ ward. The faster the kiln rotates, the faster the material is .carried forward, and vice versa.

Mr. W.H.Mason . Sheet Mo.

Third: The burden of a kiln decreases as the speed of ro¬

tation of the kiln increases. That is, the amount of material (the load) in the kiln will he less at a high speed than at a low speed. This is seen from the second statement, and can he illus¬ trated as follows:

Take two bricks, and have two kilns, A and B* kiln A mak¬ ing a revolution in 60 seconds anelB in 30 seconds. Drop a brick . at same time in each kiln. It will require a longer time for the brick to travel through A than through B. The brick will fall out of B first, vfoich is rotating the faster. Mow, if we fed one brick a second into each A and B, bricks would be dumped out of B sometime before they would emerge from A, and yet, at the instant

the first brick dropped out of B, each kiln would have .the same i»uU X't cknnnAs fiXldAjL. O imJ, iviUJL. mdaber of bricks in it. In kiln A, , and at the same rate as from B.

But A would have the heavier burden. There would be more

bricks in it, although now dropping a brick per second, the same

as B, A would be carrying more bricks, and. so have a heavier load;

the bricks would, of course, be piled deeper in the kiln. T

Beturn to the consideration of our kilns. Observations p

on one kiln will serve to illustrate the point in view in this note.

The examination of clinker from kiln Mo. 2 for the past

few days has shown plainiy^tha'need of more oxidation, while^’the '


interior, although burned hard enough, was sufficiently oxidized.

On one oocaslbn, on Dec, 3, the circumstances were as follows:

kiln cool; clinker not heated sufficiently, A short time later !

the heat increased; clinker heated hard enough; but insufficient

W.H. Mason

oxidation plainly evident. Had more air admitted, and soon noticed the kiln not so hot as before. Shut off some of the air, regain¬ ed the heat, hut oxidation not yet complete. At this point we had reached the maximum excess of air allowable for the coal being consumed, and the clinker yield was not good. It needed more oxi¬ dation. Now, if the speed of the kiln were out down Blightly, so as to compel the material to remain in the hot, oxidizing atmos¬ phere a longer time, the clinker would have been more thoroughly oxidized; this would be the oase,

Nirst: Because there would be less liability of clinkers

being formed suddenly be^ being rushed forward into the clinkerlng zone, which ocoureB when tbs kiln is running too fast. The main objection to this is that olinker bo formed balls so suddenly as to interfere with the oxidation of their interior. The outside coat¬ ing once formed prevents the oxidation of the interior.

Seoondly: Thorough oxidation is not accomplished in an instant but require b time. How long oannot be exactly said.

These are the main objections to running at a high rate of speed. Of course, too slow a speed might be objectionable, v'' resuTt/'in over-burning, but this would be erring on the side of safety. We could easily remedy that. The olaim is not made that we can put the kiln at a certain fixed speed, to be the beBt tinder all oiroumstanoes, but we do olaim that better result* oan be ob¬ tained by a lesser speed than at present, With a light burden, the kiln oan rotate faster without interfering with good burning; ample

opportunity is there for oxidation in a shorter time, but with a


Sheet No. 4

heavy burd.en a given handful of chalk, for inetanoee, has not the same opportunity for complete oxidation that the same quantity of chalk has with a light burden, each handful being subjected to same heat for the same time. In the case of the heavier burden, more time tequired.

To sum up, then, we can say a choice must be made be¬ tween these two conditions:

First: A given chalk feed; kiln rotating at a given rapid

rate and a lighter burden* The material is in the heat a shorter time, and the olinker formed more suddenly.

Second: The same given chalk feed; kilm rotating at a lesser

speed; the burden greater. The material is in the heat a longer time, and the olinker formed more gradually.

The choice must be between these two. What advan¬ tages are there in the first oase?

As a rule, in’ any metallurgical or chemical reaction where we wish to have formed some new product by combining two or more ingredients, particularly where heat is required, better re¬ sults are obtained by bringing about the reaction slowly. Sudden and violent plunging of materials into heat may serve to disinte¬ grate (and that is a good way to do it), but not to combine.

Faulty combinations oan also readily ensue from clinkering too suddenly, even though the chalk mixture be correct as a whole. In clinker formed suddenly, the union of the partioles may take place; but the complete combination or reaction of the moleoules is not facilitated.


W.H.Mason Sheet Ho. 5.

These are the principal reasons submitted in argument for a provision for a slower speed of kiln* Many other /points of a detailed nat4ure might be advanoed in favtr of it, but, belleveing the pbint sufficiently oovered by the above, 1 am, You re truly ,

(signed) E. P. Bulan

PS, - Requires 1 hr. 40 min, for passage of briok through the kiln; from aotual observation - by W.E.M. l/25/04«


The Edison Portland Cement Co,

Edison Laboratory, Orange, N.J.12/ll/03/


Mr. W. H. Maeon, Sup’t.,

Stewartsville , N, J.

Lear Sir:-

Mr. Linan's observations of the Kiln received.

1st, I do not quite understand what he means by "Insuffi¬

cient oxidation". Loes lie-mean the clinker is not oxidised? I have always understood that if the temperatures were high enough all the reactions will take place , and they will take place at the same temperature whether there be an oxidising or reducing temperature, that the clinker if in highly oxidising atmosphere will be reddish black from oxygen combining tb'. raise the iron to the ferric state, this is shown when greenish clinker is held in BunBen flame. On the contrary, if the gas is reducing the clinker will go to the green ferrous stage.

I will give several reasons why I think high speed is the best condition to produce large putput in our kilns, say 2 revolutions per minute, but they are only arguments and theory and very little reliance should be placed on them in view of the fact that we have every means to experiment and let results bring out the proper theory and method.

Arguments for high speed.

' 1st. Lighter load per foot hence pressure on itself in

sticky state will cause it to ball less or if balled the mass will be more porous. A sticky mass 6 inches thick will have a pressure on the bottom iayer due to the weight at that height; if one foot thick it will have twice the psessure, hence the tendency to ball up is greater and in addition the extra weight acting on what is balled will make it more dense by continuous pounding by its ovm in¬ creased weight. In addition, when the larger masses enter the strong clinkering zone they will break up into finer balls if the load is 6 inches thati-they would if the load was 12 inches as the porosity will be less in the latter case. Therefore, if the balls are larger and in addaition more dense, they will not burn ti-o the centre so rapidly hence the heavy load balls will require more time .

2nd. The passage of brick through the kiln is not criter¬

ion of the speed of the chalk and clinker for the reason that a brick can only progerss by the action of the angle of the kiln,

Mr. W.H.M.

whereas the chalk on account of hulk, air ani. explusion of C03 blowing up and the. fomation of the ring at chalk and produce a congestion and raise the angle line far above the normal grade of the balance of the stock and there is continual avalanches of ma¬ terial which causes it to advance twenty to fifty feet in a single revolution of the kiln, whereas the brisk would not more but a few inches; now with a fixed load, if you slow the kiln to half, the chalk hill doubles in altitude and the tendency and distance in which the stock will avalanche ahead is greatly increased and proceeds so far into the clinkering zone that it gives off C02 to disturb the proper combustion of the coal, for the reason that coal will not burn at all when the proportions of CO to C02 reaches 33 volumes of CO to 66 volumes' of C02, no matter if you have plenty of oxygen just as in a blasjr furnace KhaaixJthRxkiststfcxSsr- jaasus when the vbihumes of CO to C02 as stated, is reached no fur¬ ther reduction of iron ore can take place. Therefore, to get good economy, good combustion and high tempenature , it is very desirable that the principle proportion of the C02 should be driven off be¬ fore it gets hear the clinkering zone, but the avalancing movements prevents it, the greater the load, the greater the avalanching and projection of unprepared chalk into the clinkering zone to disturb your combustion, lower the temperature and produce badly burned clinker.

3d: Now if the chalk ring formed at chalk end builds up to the same height with a light load as it does with a heavy load, then there would be no gain in speeding the kiln when the chalk feed was constant because the avalanching will be just the same, and the principal resaofi. f or speeding would be nullified and these ar¬ guments fall to the ground.

4th: Could the formation of this ring be prevented there would not be any avalanching Toy£& steady even progression of the stock and at 2 revolutions per minute there would be ample time for the heat to penetrate to the centre of the balls on account of the long zone of high temperature , cement clinker is very good conductor of he&tY-the centre of cube of one inch will reach that of the outside in a few minutes, and the reason so many come through th e kiln with centres which have never reached the temperature

of low "temper at ure" chalk rusnell Y6rTtop of it by the avhlancheaat times get excessive it brings so much C02 into the combustion one that you will lose your heat no matter how much coal you put on.

We will be met by this mechanical difficulty every time we try to increase the load beyond a certain point in our kilns, say 30 to 32 barrels beyond that amount the avalanche will project itself further into the combust! organa limit the output by making it impossible to burn the coal by the C02 produced, and the only way to increase the ouput is to stop or reduce the avalanching at the back ring and I told Mason to speed the kiln upon the theory that the height of the ring and load would be less and . thus re¬ duce the avalanches so the greater load can be carried.

6th. The time required to burn cement i& purely a ques¬

tion of temperature and heat conductively of the mass; and inch cube can be burnt perfectly to the centre in twenty minutes in a gas furnace if its attempted to burn it in less time -by raising the tenperature, the outside will start to melt. I do not. think it would be burned any better if it was in an hour. The reactions are not forced reactions except exclusion of C02, they would take place at ordinary temperature of themselves if they were viscous. The only functions performed by heat after explusion of C02 is to soften their ingredients so their molecules can act. When this soft atage is reached the reactions can take place, any increase in the softening does no good. The finer ground the materials are, the less the softening required aid the lower the temperature: if the particles are corase ground, it would be necessary to raise tlrthe clinker to a semi-fluid condition to get combination of the coarser particles'.

Could the gun be used at the chalk end to break up the ring and stop or reduce avalanching, you could easily raise the output but I suppose this is not practicable.

Yours truly.,

Sigd. Thos. A. Edison


Jan. 8, 1904.


Mr. W. H. Mason, Supt.,

The Edison Portland Cement Co.,

Stewartsville, N. J.

Pear Sir:-

The letter of Mr. Edison's relative to the operation of the kilns, contains, besides much valuable information a few statements which do not 'quite agree with results we have sot f dree", obtained with the kilns. As well as not quite conforming to demon- strat wire suit s , hitherto obtained in general practice. Neither can I see how. they can stand theoretically, and wish to call your attention. to the same. It is agreed, of course, that it is best to let actual ptaatiiaib results being out the best methods.

The insufficient oxidation of clinker mentioned .

' *•**>.,, "■ . : ; in letter of December 4, 1903, applied to the interior of the clink¬ er chiefly. This fault of the clinker has been the case on differ-, ent occasions, and as was before stated^ is be li eyed due to the rate at which the material is propelled through the kiln. The exterior of the clinker in nearly all cases was sufficiently oxidized, i.e. the reactions were .completed. The interior in many cases was not.

Iii some' >cases the exterior showed the effect- of prolonged heating ..after formation and; had a. thin reddish brown coating. In the clink-, er with faulty interior the combination of the lime with silica and

YT.H.M . 2 1-8-04.

alumina is not complete; the sulphur present in some cases existing as sulphide of lime which should, not be. Such sulphur should be. converted to suplhate of lime. To do this, requires oxygen, necessitating air, and it takes time to do it. It must be understood that to make Portland Cement clinker, an oxidizing at¬ mosphere is necessary, together with a high temperature.

Take good clinker and heat in the Bunsen flame, in either the oxidizing or reducing part, and a reddish fcrown color will be noticed on the surface. Note that this takes place in either the oxidizing or reducing flame of the Bunsen bunner. I believe it to be nothing more than a separation of the ferric oxide, due to the heating, from whatever state of combination in which it may have been. Supposing the greenish colored clinker has ferrous iron ■which can be changed to ferric iron, this does not prove that all the iron in that clinker is ferrous iron. The fact is, practical¬ ly none is found in the cement, so it could hardly have been in the clinker.

There is a time when some of the dfcbnkis in the ferrous state. This is when ferric oxide is uniting to silica. In the chalk iron exists under the two conditions, ferrous and ferric, chiefly in the latter state. In much of the rock of this xection, or belt, sulphide of iron is present; .it can easily be seen with the naked eye. This much alone could account f on the ferrous iron. There could also be present ferrous silicate, but likely very little of it. The most of it is in the ferric form. Cer¬ tainly some of this ferric oxide reacts with the selica, even in the presence of the large quantity of lime. It is an established fact that ferric oxide and silica cannot, unite directly. Berric

W.H.M . 3. 1-8-04.

oxide must first break down to the ferrous state which it does by heat, according to this equation Pe2<)3 s gPeO +■ 0. The fer¬ rous oxide then united with silica to form the different silicates of iron. At this stage the presence of ferrous iron is accounted for but this could hardly apply throughout the whole piece of clin- . ker .

The uni-ferrous silicate melts at about the melting point of cast iron; when suddendly cooled it forms into crystals of dark olive green color. The bi-ferrous silicate melts at about the melting point of steel; it is flesh colored when cooled. The tri-ferrous silicate is still less fusible, remaining viscous at a white heat.

We are more likely to have the uni-silioate or the bi¬ silicate. Note that the colors are olive green and flesh colored, colors noticed at times on the outside clinker. It also requires ' quite a high heat to bring about the reactions of ferric oxide and silica. Also ferrous silicates readily decompose in the air yielding ferric oxide and silica.

Now remembering the great preponderance of lime over oxide of iron, to react with the silica; the small percentage of oxide of iron present; the fact that practically all the iron present is in the. ferric state; and the difficulty attendant upon the reaction of the ferric oxide with silica, it bein£ performed in the case of Portlahd Cement clinker, in an oxidizing atmosphere, the chances are that very little silicate of iron is present, and it cannot readily be understood if the oxygen of the air in a short time can decompose ferrous silicate, why the highly oxidizing heat

Mln. doggLngt accomplish this almost. -Irmtarrhl-u-. i„m.^

V.H.JJ. . 4.

very little chance for the presence of ferrous iron in the clinker, it could he believed that some ferrous iron might re suit from. the partial combustion of coal in contact with it, coloring the exter¬ ior hut we have first to get proof that the iron is present in the ferrous state. From the fact that the uhi-ferrous silicate is olive green colored; and that clinker is olive green colored, it does not follow that the iron in the clinker is in the ferrous state; there are other substances in the clinker besides the iron