THE AMERICAN 



MONTHLY 



MICROSCOPICAL JOURNAL 



YOL. III. 



New Yoek, Septemtjek, 1882. 



ISTo. 9. 



American Association for the 

 Advancement of Science. 



SECTION OF HISTOLOGY AND MICRO- 

 SCOPY. 



The meeting of the American As- 

 sociation for the advancement of Sci- 

 ence was held this year at Montreal. 

 It began on the 23d of August and 

 continued one week. About one 

 thousand members attended the 

 meeting, and some of the papers read 

 were of great scientific value. 



In the section of histology and mi- 

 croscopy, as v/ell as in some of the 

 other sections, papers were presented 

 on subjects of interest to microsco- 

 pists. In the following report of the 

 meeting, notices and abstracts of the 

 papers read pertaining to microscopy 

 will be found. 



Prof. Wm. H. Brewer read a paper 

 before the section of physics, entitled 



APPARENT SIZE OF MAGNIFIED 

 OBJECTS, 



in which he gave the results of a long 

 series of experiments on the apparent 

 size of the image formed in the micro- 

 scope, as seen by different persons. 

 About 440 different persons were 

 questioned as to the size of the im- 

 ages of various objects, but finally a 

 small insect was selected as the test- 

 object. The actual length of the im- 

 age, as drawn by the camera lucida, 

 using a i^-inch objective, was 4.66 

 inches, including the antennse, 4.87 ; 

 the diameter of the field was 5.85 

 inches. 



The results may be briefly summed 

 up as follows : Of the 440 persons, 

 about 41, or g 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. 

 The greater number of persons under- 

 estimated the size ; 2 estimated it at 

 less than one inch, 7 made it over a 

 foot, 45 made it 2 inches, or less, 22 

 made it 10 inches. The largest esti- 

 mate was by a mechanic, who said it 

 looked like a picture projected on a 

 screen and it seemed to be five 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. 

 The subject was briefly discussed, 

 and Mr. LeConte Stevens made a 

 few remarks upon the physiological 

 aspect of the matter, which will be 

 given next month. 



Dr. B. W. Carpenter, of London, 

 being present at the meeting, was re- 

 quested to address the section of 

 microscopy. A large audience assem- 

 bled on Friday afternoon to hear the 

 views of the eminent microscopist 

 upon the subject of the best objectives 

 for biological work. He spoke with- 

 out notes, and the report given below 

 is believed to be as full and as accur- 

 ate a summary of his remarks as 

 could be obtained without the aid of 

 a stenographer's report. 



DR. B. W. carpenter's ADDRESS. 



This address was quite popular in 

 character — well-adapted to the audi- 

 ence assembled, which included many 

 persons not familiar with the micro- 

 scope. The speaker said he would 

 attempt to give the results of what 

 has been going on in Europe and 

 America — both practical and theo- , 



