PROCEEDINGS OF THE SOCIETY. 261 



MEETING 



Held on the 16th of March, 1004, at 20 Hanover Square, W. 

 Dr. D. H. Scott, F.R.S., etc., President, in the Chair. 



The Minutes of the Meeting of February 17, 11)04, were read and 

 confirmed, and were signed by the President. 



The following Donation to the Society was announced, and the 

 thanks of the Society voted to the donors. 



From 

 Hutton, F. W., Index Faunae Novae Zealandice. (8vo, London, 1904) TJte Puhlisherg. 



Prof. A. E. Wright communicated the purport of his paper, ' On 

 some new methods of measuring the magnifying powers of the Micro- 

 scope, and of its separate elements,' illustrating his remarks with a 

 lantern diagram of a new piece of apparatus termed the Eikonometer, 

 and by numerous drawings on the board. 



Mr. J. W. Gordon said this paper had no doubt conveyed to most of 

 the Fellows present a very comprehensive view of the available methods 

 of ascertaining the magnifying power of the Microscope, and they would! 

 certainly have appreciated the extreme simplicity of some of these. But 

 with regard to the point which Prof. Wright had touched upon in dis- 

 cussing the second method described — he adverted to the question as to 

 at what point it was proper to divide up the Microscope into sections for 

 obtaining the separate values of each — Prof. Wright's view seemed to be 

 that there was no need to pay any attention to the view plane of the 

 image itself, and it seemed perfectly clear that for the purpose of arriving 

 at the magnifying power it is unimportant at what stages they made the 

 rests in dividing up the instrument into parts. Prof. Wright said it was 

 convenient to consider the objective by itself, and then the eye-lens and 

 the field-lens, and to estimate their magnifying powers and to put these 

 together. It seemed to him it was convenient also for another reason, 

 that they knew very approximately what was the power of the objective, 

 and they were usually much more at home with this than with the 

 ocular, which was a much stranger portion of the instrument than the 

 objective which they had more frequently to make choice of. On the 

 other hand, it occurred to him that there were certain conveniences in 

 being able to determine the magnifying power in the view plane of the 

 instrument. The reason was, that for some purposes, especially for the 

 purposes of photography, they had to get rid of the magnifying power of 

 the eye-lens altogether, and in that case it was a manifest advantage to 

 be able to tell the magnifying power of the real image formed in the 

 instrument itself. 



With regard to the new instrument which had been shown to them 



