1883.] 



MICROSCOPICAL JOURNAL. 



173 



in another similar apartment Col. A. 

 E. Stevenson exhibited a variety of 

 well prepared objects, by means of 

 his projection microscope, made by 

 Dr. Hugo Schroeder, of Hamburg, 

 and which is said to have the largest 

 prism ever cut. The thanks of the 

 societies are due to the Calumet Club 

 for their courtesies, and especially to 

 Mr. B. F. Nourse, chairman of the 

 Committe on Soiree, for the very com- 

 plete and happy arrangements and 

 management of the affair. 



During the course of the meeting 

 several important reports were re- 

 ceived. The committee on nomen- 

 clature and sizes of eye-pieces, R. H. 

 Ward, chairman, rendered a report, in 

 which it was recommended : i. "That 

 oculars, like objectives, be named by 

 their equivalent focal length, in Eng- 

 lish inches." The report continues : 

 " We believe this method to be the 

 best adapted to practical use, suffici- 

 ently precise for its object, and capa- 

 ble of general introduction with less 

 inconvenience, opposition or delay 

 than any other rational system." 2. 

 '• We report in favor of adopting one 

 or more standard sizes for the tubes of 

 oculars . . . As an important step 

 towards uniformity, we would gladly 

 recommend the adoption of the sizes 

 recently proposed by the Royal Micro- 

 scopical Society, 0.92 and 1.35 inches, 

 were they adapted to the conditions 

 existing in this country. But .92 in. is 

 a smaller size than we are willing to 

 recommend for any purpose, being 

 much too little, in our judgment, for 

 even the small compact stands of the 

 ' Continental ' model. On the other 

 hand we would have preferred 1.40 in. 

 for the large tube, but do not regard 

 the dilTerence as sufhcient importance 

 to justify the naming of still another 

 size. There remains, however, a very 

 large variety of medium-sized stands, 

 a class believed to be rapidly increas- 

 ing in number and importance, which 

 cannot, without total change of -char- 

 acter, be raised to 1.35 in., and which 

 should not, in our opinion, be reduced 

 even to i in. We therefore propose a 



standard medium size, 1.25 in., which 

 we believe well adapted to a great 

 majority of purposes, with the alterna- 

 tives of I in. and 1.35 in. for those who 

 wish a smaller or a larger size. . . . 

 We would also recommend that 0.75 in. 

 be made a standard for the upper tube 

 of the ocular. We would also recom- 

 mend the adoption of the diameter 

 1.50. in. recommended by the Royal 

 Microscopical Society for substage 

 tubes." The report will be printed 

 in the Proceedings, and receive further 

 consideration next year. 



Prof. Rogers, who represents the 

 Society in the general committee on 

 Micrometry, Prof. Barnard, chairman, 

 presented an exhaustive report upon 

 "Standard Centimeter A, 1882," ob- 

 tained from Prof. Hilgard, director of 

 the United States Bureau of Weights 

 and Measures. This particular plate 

 is of piatinum-iridium, united to brass 

 by silver solder. It is now the prop- 

 erty of the American Society of Micro- 

 scopists ; the National Committee on 

 Micrometry having received it from 

 the Bureau of Weights and Measures, 

 in turn, tendered it to the Society ; it 

 was accepted and adopted as a basis 

 of future studies and discussions in 

 micrometry. It is now in the custody 

 of Dr. Fell, and rules for its use and 

 control will soon be published by the 

 committee appointed for the purpose, 

 and for securing copies on glass. 

 Prof. Rogers said of the plate, " In 

 the examination with a half-inch ob- 

 jective supplied with Tolle's opaque 

 illuminator, it became at once appa- 

 rent that the defining lines are of the 

 most beautiful character. I do not 

 think I ever succeeded in producing 

 Jines upon a metal surface quite equal 

 to the lines upon this plate." The 

 original basis of comparison with the 

 micrometer is a meter upon copper, 

 prepared for Prof. Rogers by Prof. 

 Tresca, of the Conservatorie des Arts 

 et Meters of Paris. The results of 

 the comparison of the piatinum-iridium 

 centimeter and the one-hundredth of a 

 meter traced on glass, and those re- 

 lating to the comparison of the micro- 



