52 



SCIENCE. 



A PLEA FOR THE METRIC SYSTEM IN 

 MICROSCOPY. 



By R. H. Ward, M. D., Pres. Am. Soc. of Micr. 



One of the most important questions, theoretical and 

 practical combined, which is now fairly before the micros- 

 copical world and still in an unsettled state, is that of gain- 

 ing definiteness and uniformity in micrometry. In this field 

 emergencies have arisen during the past year which have 

 compelled me to take considerable responsibility, as well as 

 to perform a large amount of work, trusting that the gene- 

 rous approval of my colleagues would accept and ratify 

 what seemed at the time, and what seems now, most con- 

 sistent with the interests of science and the dignity of this 

 body. It will be remembered that a year ago, just at the 

 close of our Indianapolis meeting, resolutions were offered 

 favoring the metric system for micrometry, and the one 

 hundredth of a millimeter as the unit to be employed, inviting 

 foreign co-operation, and accepting an offer of standard 

 micrometers from Prof. William A. Rogers, of the Astron- 

 omical Observatory of Harvard University. None of these 

 points, save the last, were new or unconsidered. They had 

 been studied at leisure for years by many members who were 

 present. The metric system had been adopted by all the world 

 except Russia, England and the United States; and its univer- 

 sal adoption was, as a rule, earnestly desired and favored by 

 the educated and scientific classes. It had been adopted, or 

 recommended, after mature deliberation, by the National 

 Academy of Sciences, the American Metrological Society, 

 the American Association for the Advancement of Science, 

 by the American Society of Civil Engineers, the United 

 States Coast Survey, the United States Marine Hospital 

 Service, the American Medical Association, the Congress 

 of Ophthalmologists, and by the largest State and local 

 Medical Societies and by leading Medical Schools and 

 Journals, by numerous Boards of Education, College 

 Faculties and local Scientific Societies, and by experts in 

 i arious branches of science and art. On the other hand the 

 lesolutions contained some minor faults, mostly in matters 

 of taste or tact, which could have been easily remedied by 

 reference to a committee. But there was no time for refer- 

 ence or for adequate discussion, and rather than discourage 

 their object by failure or postponement, they were adopted 

 and referred to the local Societies for consideration. They 

 were passed unanimously, at a small session, it is true, but 

 by the same vote which established this society and author- 

 ized its meeting here to-day. As too often happens, their 

 incidental faults attracted more attention than their really 

 scientific object. The unit proposed was evidently too 

 long for integers and too short for fractions, and unlikely 

 to receive a single approval either at home or abroad ; the 

 proposal of international action, though its object was uni- 

 versally approved, was in a form not likely to accomplish 

 that object ; and the liberal offer of Prof. Rogers was wholly 

 misunderstood and perverted, until it took the form of the 

 preposterous statement that it was proposed to make Prof. 

 Rogers' micrometers standard as distinguished from those 

 of other (!) makers, not the least amusing of all the blunders 

 and absurdities of this precious statement being that of 

 bringing the association, in any manner, by trade rivalry 

 or mercenary considerations in relation with the work 

 of one of our most generous scientists who has freely 

 shared with the public every result of his labors, while 

 pursuing them at an extravagant cost, and without a 

 thought of pecuniary return. It soon became evident 

 that an organized treatment of the subject was required 

 to secure a proper and unprejudiced discussion of the 

 objects of the resolutions. Feeling much responsibility as 

 the presiding officer of this Society, and of one of the 

 oldest of the local Societies, but having no authority to ap- 

 point ail evidently necessary committee that should repre- 

 sent not only this Society but also sections of the country 

 not yel named upon our rolls, I brought the subject before 

 Out local Association, and we invited all the Societies that 

 could be reached to join with us in the selection of a 

 National Committee for the consideration of this subject. 

 The response from the large and active Societies, and from 

 distinguished individuals, was a cordial and almost unani- 

 mous approval. Many of the Societies nominated to the 

 committee members distinguished as specialists in this 



branch of microscopy ; both Societies and eminent scientists 

 contributed valuable opinions upon all the points at issue ; 

 and a large committee was organized which will, at a proper 

 time, tender a report of progress to this Society. And 

 while speaking of this committee, I will take the liberty of 

 saying that it would be a pleasure to me, and I doubt not to 

 all of us on this side of the lakes, if our friends from Tor- 

 onto or Montreal, or any other points in the Dominion which 

 may be represented here, would nominate members, and 

 thus make it an American instead of a national body. To 

 prevent confusion or misapplication of the practical sug- 

 gestions which follow, and which naturally belong to this 

 time and place, it is necessary to anticipate the report of the 

 committee so far as to say that it will recommend to this 

 Society to rescind its approval of the one-hundredth of a 

 millimeter as the unit of micrometry, and to so modify the 

 forms of the other resolutions as to leave the important 

 questions of accurate measurement and convenient and 

 scientific nomenclature in a favorable form for the attain- 

 ment of valuable results. 



Whether this Society, as such, shall continue to be known 

 as actively interested in this reform, it is for you to say ; 

 though I sincerely hope that the members will unanimously 

 agree with me in judging that it ought to do all that its in- 

 fluence, without dictation, can do in this direction. But I 

 for one do not deem the decisions of Societies or other cor- 

 porate bodies decisive and final. I am not much elated by 

 their approval, ordiscouraged by their opposition. I have 

 an average amount of respect for the motives but not for the 

 efficiency of legislation. In State, in Church, in Science, 

 it is possible and easy to carry out laws about in propor- 

 tion as they are unnecessary. People who do not need 

 government are easily governed. Persons who appreciate 

 authenticated micrometers will use them if they can, with or 

 without the approval of societies ; and those who do not 

 desire them will be about as little controlled by official 

 decisions. While the encouragement and support of 

 Societies and officials are welcome and valuable as far as it 

 extends, I have more faith in the power of individual in- 

 fluence, and to that I look for an example which is able to 

 settle this question beyond appeal. 



In our micrometry we have the anomaly of a system of 

 work capable of a precision almost, if not quite, unknown 

 elsewhere to human art, for what other wholly artificial pro- 

 cedure possesses a demonstrated limit of accuracy inside 

 of the i-300,oooth of an inch, and yet, until now, we have 

 made no reasonable effort to free ourselves from avoidable 

 errors known to be many times larger than that amount. 

 While coal at $4.00 a ton and muslin at six cents a yard are, 

 or at least pretend to be, measured with apparatus that has 

 been carefully verified by standards of known quality, we 

 have been measuring spaces almost infinitessimally small 

 by standards of only commercial quality and possessed of 

 manifest and uncorrected errors. This fact is too sugges- 

 tive of the days when micrometers consisted of grains of 

 sand and clippings of wire ; with the odds against us that 

 we know how to do better. Arrange your microscope so that 

 it will magnify 3,000 or 4,000 times, making the one-thous- 

 andth of an inch on the stage seem three or four inches 

 long through the lenses, then arrange an ocular micrometer 

 so that the magnified one-thousandth of an inch shall be 

 covered by, for instance, one hundred divisions of the 

 ocular scale, and finally ascertain exactly how many of the 

 one-thousandths of an inch on that or any other plate will 

 be similarly measured by precisely the same one hundred 

 divisions above it. Judging from my experience and from 

 that of others who have tried the experiment, you will 

 probably find a perfectly measurable discrepancy between 

 the different spaces of the same name ; so that even your 

 own measurements, with the same apparatus, will not be 

 comparable with each other unless, as is often done, you 

 select some one average space as a basis of comparison, 

 and are careful to use only that. Now we are trying to as- 

 certain which of these various spaces is the correct one ; 

 or if not one is right, then to obtain one that shall be ; or if 

 that can not be done, at least to determine a known error 

 from which we can compute definite results. This is not a 

 question of makers, or dealers, or trade interests in any 

 form, but of unmixed and independent science. We are 

 attempting to procure a standard because we need it, and 

 we hope for the cordial assistance of microscopists of really 



