PROCEEDINGS OF THE SOCIETY. 227 



The Chairman said that, apart from the fact that this was a portrait 

 they were very glad to possess, he thought it was of great interest as 

 being an extremely beautiful specimen of the style of engraving which 

 was in vogue at the period when this was printed, and which was of 

 high excellence. 



The thanks of the Society were, upon the motion of the Chairman, 

 unanimously voted to Mr. Curties for his donation. 



Mr. E. M. Nelson said that two old Microscopes which had recently 

 come into the Society's possession were of considerable interest. The first 

 Microscope, a non-achromatic, was purchased by the Society ; it has the 

 name of Carpenter, 24 Regent Street, engraved upon it, and its date 

 may be assigned to about 1825. It is especially interesting from the 

 fact that the late Hugh 1'owell, before he began to make Microscopes 

 on his own account, used to make them for the trade, and there was no 

 doubt that they had an early specimen of Hugh Powell's work before 

 them. It was a great acquisition to the Cabinet of the Society, as they 

 did not already possess one of this particular type. 



The other Microscope, kindly presented to them at the last Meeting 

 by Mr. Kern, was one of the Scarlet and Culpeper type, and is in a 

 remarkably fine condition, seeming as if quite new from the hands of 

 the makers. It is signed " Dollond," and in the box in which it is 

 packed there is a printed description, which bears the names of John 

 and Peter Dollond of St. Paul's Churchyard. John Dollond, the father, 

 was a silk-weaver by trade, but, having turned his attention to mathe- 

 matics, he gave up silk-weaving and joined his son, who was an optician ; 

 in 1758 he received the Copley medal for the invention of the achro- 

 matic telescope, and died in 1761. If, therefore, this Microscope was 

 made in his life-time, its date is fairly well determined. 



The Secretary said they had received from Messrs. Staley and Co., 

 the agents of the Bausch and Lomb Optical Company, for exhibition, 

 a Bausch Camera Lucida, which was described in the Journal last year 

 (volume for 1900, p. 734). It was only indirectly connected with the 

 Microscope, and was apparently intended to help people to draw small 

 objects which they were unable to copy otherwise. 



Mr. E. M. Nelson read his paper on ' The Working Aperture.' 

 The Chairman invited discussion upon the subject of this very 

 interesting paper, which he ventured to think was one which most 

 microscopists had greatly neglected. 



Dr. Tatham said he was very glad that Mr. Nelson had brought 

 this matter before them in his usually concise and practical way. 

 Dr. Tatham had himself experienced the difficulties described, and had 

 tried to overcome them, but although he had not formulated his own 

 difficulties in the same way as Mr. Nelson, he had often experienced 

 the uncomfortable feeling that when, after a great effort, he had ob- 

 tained a particularly good resolution of a difficult object, it was uncer- 

 tain whether he should be able to reproduce it on a subsequent occasion. 

 By showing them how this could be done with accuracy and certainty, 



