ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 861 



r, the refractive index of the glass piece; a, half the crown-glass 

 angle of the objective." 



Apparent Size of Magnified Objects.* — Prof. W. H. Brewer read 

 a paper before the Section of Physics, at tbe Montreal Meeting of 

 the American Association for tbe Advancement of Science, in wbich 

 he gave tbe results of a long series of experiments on tbe apparent 

 size of tbe image formed in tbe Microscope, as seen by diiferent 

 persons. About 440 different persons were questioned as to the size 

 of the image of various objects, but finally a small insect was 

 selected as tbe test object. The actual length of the image, as drawn 

 by the camera lucida, using a H-inch objective, was 4 '66 inches, 

 including the antennae, 4*87; the diameter of the field was 5*85 

 inches. 



Tbe results may be briefly summed up as follows : — Of the 440 

 persons, about 41, or 9 per cent., judged the size quite correctly; 

 82 of them, or 19 per cent., made the size 4*25 to 5 inches, which was 

 reasonably good. Tbe greater number of persons underestimated tbe 

 size ; 2 estimated it at less than 1 inch, 7 made it over a foot, 45 made 

 it 2 inches, or less ; 22 made it 10 inches. The largest estimate was 

 by a mechanic, who said it looked like a picture projected on a screen 

 and it seemed to be 5 feet long. Experience seems to correct false 

 estimates, as was illustrated by three estimates by a gentleman who 

 used the Microscope in drawing ; in three successive years his 

 estimates were respectively 9, 8, and 7 inches. 



Committee on Ruled Plates. — At the meeting of tbe Section of 

 Histology and Microscopy of tbe American Association for the 

 Advancement of Science, at Montreal, after the reading of a paper by 

 Professor W. A. Rogers on ruled lines, a resolution was proposed that 

 a committee be appointed to receive ruled plates from different makers 

 that might be offered for examination in accordance with the sug- 

 gestions made by Professor Rogers. After some discussion the 

 resolution was carried, but it was afterwards decided to postpone the 

 appointment of the committee until some future time. 



Professor R. Hitchcock regards this t " as a great step toward the 

 settlement of the question of the practical limit of resolution, inde- 

 pendent of any theoretical considerations," and " hopes and believes 

 that at the next meeting of the Association a committee will be 

 appointed." 



Quekett Microscopical Club. — It has been determined to give a 

 series of demonstrations upon elementary subjects connected with 

 Microscopy on the " Gossip " evenings of this Club. Tbe first six 

 will be on tbe following subjects : — Dec. 8, 1882, Tbe History of a 

 Stained Section of an Animal Structure, by Mr. J. W. Groves. 

 Jan. 12, 1883, Photo-micrography, by Mr. T. Charters White. 

 Feb. 9, Sea-side Collecting, by Mr. A. D. Michael. March 9, Some 

 Methods of Preparing Parts of Insects for Microscopical Examina- 

 tion, by Mr. E. T. Newton. April 13, Microscopical Vision, by Mr. 



* Amer. Mon. Micr. Joura., iii. (18S2) p. 161. 

 t Ibid., pp. 197-8. 

 Ser. 2.— Vol. II. 3 M 



