PROCEEDINGS OF THE SOCIETY. 349 



any body of microscopists to adopt tlie -j-^^ of a millimetre for the 

 standard as had been recommended. 



Dr. Edmunds in seconding the resolution said that the y^^ of a 

 millimetre was clearly too large, while the yoVo being less than one- 

 seventh the diameter of a human blood-corpuscle, showed that it was 

 sufficiently small for all the work of practical histology. 



Mr. Stephenson said that he entirely agreed with the views which 

 Mr. Crisp had expressed as to the y^^y of a millimetre, which was 

 obviously much too high a standard, leading as it constantly would to 

 the use of fractions of the unit which it ought to be one of the essential 

 qualities of a standard to avoid. At the same time ho considered that 

 the time had not arrived when they ought to formulate in a resolution 

 a positive injunction as to the use of any given standard. So far as 

 that was desirable, it had already been done by the Leyden resolution 

 of Professor Suringar He would therefore move — 



" That in the opinion of this Society, the yj q- of a millimetre is 

 too large a unit for micrometric measurements, and that it is 

 not expedient at present to prescribe by any formal resolution 

 the adoption of a fixed standard for micrometry." 



Mr. Michael thought that if they were to have a standard at all 

 the one proposed was perhaps the best to be adopted. But the ques- 

 tion in his mind was, whether it was desirable or convenient to 

 establish a special standard for the purpose of microscopy alone? 

 The greater part of the work requiring measurements was done by 

 those who engaged in it as a part of their ordinary work, and in such 

 case it would be difficult to say what was microscopic work to which 

 this new standard was to apply in place of the ordinary methods of 

 measurement. He thought therefore that the adoption of a new 

 standard required very grave consideration. 



Mr. Curties was certainly not in favour of attempting to come to 

 any decision now as to the adoption of a standard. 



The Chairman, having put the amendment to the Meeting, declared 

 it to be carried. 



A letter from Professor E. Hitchcock, of New York (of 12th 

 March), as to standard micrometers, was read by Mr, Crisp, of 

 which the following is an extract: — "As to standard micrometers, I 

 cannot understand why there is so much ojiposition to adoi)ting a 

 standard division. I believe that such a divison will be adopted here, 

 and that the metric system will supersede all others. It requires only 

 a slight familiarity with micrometers ruled on this system to convince 

 anyone of their superiority. As to the question of accuracy, I assume, 

 and with propriety, that divisions of yJo^ mm., or yo^tr iiich, can 

 be ruled so that the variations from a given standard are measured by 

 milliontJis of an inch, varying from i to ±25 millionths at a 

 given temperature. I have a " standard cm," in which the average 

 variation in the spacing is not far from 10 millionths of a mm., 

 according to the determinations of Professor Rogers, the maker. (I 

 speak from memory ; it may be a little more than this, but some of the 



