QUEKETT MICROSCOPICAL CLUB. 257 



exchange of water takes place. Mr. Traviss also exhibited a 

 very convenient and portable form of siphon-strainer. 



Several members testified as to the efficiency of Mr. Traviss's 

 apparatus, which he used at the last excursion of the Club 

 (June 21st). 



A paper " On a New Method of Measuring the Magnifying- 

 power of a Microscope," communicated by Mr. E. M. Nelson, 

 F.R.M.S., was read by Mr. J. Grundy. 



After reading Mr. Nelson's paper, Mr, Grundy offered a few 

 remarks of his own. 



Mr. Grundy exhibited a modification of the photomicrographic 

 camera projection method. A light cardboard tube of about 

 24 in. diameter and about 12 in. in length fits loosely over the 

 eye-piece ; the other end is supported by a clamp-stand. (The 

 microscope may be in any position; inclined is most convenient.) 

 At a distance of about 10 in. from the lower end a circle of fine 

 ground-glass is fitted. This is carried in a " draw-tube," per- 

 mitting correction for the position of the Ramsden disc for 

 various eye-pieces or for different tube-lengths. If a micrometer 

 is placed on the stage the projected image may be observed on 

 the ground-glass, and the divisions gauged with dividers, and 

 compared directly with an ordinary rule. Mr. Grundy also 

 exhibited microscopes fitted with Beale's neutral-tint camera- 

 lucida, Ashe's modification of Beale's form, and a Wollaston 

 model. 



The President said they were much indebted to Mr. Nelson 

 for his paper, and to Mr. Grundy for reading it. He had himself 

 very often to make microscopical measurements, and though no 

 doubt the method described was very good in theory he did not 

 know how it would work out in practice as compared with the 

 very simple method which he was accustomed to adopt namely, 

 by drawing the object with a Beale's camera, and then in the 

 same way drawing the micrometer scale when placed on the 

 stage in place of the object. By applying these to one another 

 he could measure a thing in a very short time, and did not see 

 how he could possibly go wrong in so doing, although there might 

 be a slight distortion caused by the eye-piece. 



A cordial vote of thanks was accorded to Mr. Nelson for his 

 useful paper, and to Mr. Grundy for the interesting way in 

 which he had brought the paper before the Club. 



Journ. Q. M. G, Series II. No. 73. 18 



