3t) PROGRESS OP MICROSCOPICAL SCIENCE. 



case it would require a few pins to serve as legs. The want of paral- 

 lelism is less than in most compressors, and is not inconvenient in 

 clinical use. The two brass plates separate entirely for arranging the 

 object or cleaning the glass. The upper plate fits into a notch filed 

 in a ledge at the left of the lower, the centering of the two plates 

 being secured by a pin through the lower and a notch in the upper. 

 The screw which attaches them at the right is permanently fastened 

 in the upper plate by a groove and a pin. It has a coarse thread, 

 which may be cut double to screw out more rapidly, or the thread may 

 be reversed near the centre so that it will at the same time raise the 

 upper and depress the lower plate. Should a steadier motion be re- 

 quired, a spring may be riveted upon one plate to press against the 

 other. The apparatus is adjusted for a glass of g^gth inch below the 

 object and y-rr^th above, cemented upon the inner siu'face of the brass 

 plates. This is strong enough to carry in the pocket safely ; it can 

 also be used with the parabolic illuminator, or with any objective or 

 achromatic condenser except those of large angular aperture. Should 

 thin glass be required for any purpose, a glass or tin cell of sufficient 

 thiclmess to make up the difierence should be cemented on one of the 

 plates, or both if necessary, and the thin glass fastened upon the rim 

 thus formed. Should no cell of suitable thickness be at hand, select a 

 glass cover of the required thickness, fasten it with marine glue on one 

 of the plates, punch out with a file the part corresponding to the open- 

 ing in the plate, and then fasten the thin glass with Canada balsam 

 upon this extemporized rim. 



A Gundlach's Microscope. — Mr. E. B. Benjamin, of New York, exhi- 

 bited a microscope by Gundlach of Berlin. This was a small and cheap 

 instrument, according to the English and American standard, but 

 really admii-able for its neatness of design and finish, and its general 

 excellence of performance. 



A New Locality for Trocheta suhviridis. — In February, 1869, 

 T. suhviridis was found by Mr. Heniy Lee, F.L.S., F.E.M.S., in the 

 neighbourhood of Horsham, Sussex. Now he has found it in another 

 locality. In ' Land and Water ' the following account occurs : — " I 

 have now the pleasure of announcing that I have found Trocheta suh- 

 viridis abundant in another locality, namely, on the Beddington 

 Sewage-Irrigation Farm of the town of Croydon, Surrey, and I am 

 informed that this leech is also to be foimd on the other irrigation 

 land belonging to the same town at Norwood. The experiences of 

 naturalists have differed respecting the capability of Trocheta of living 

 for any length of time completely immersed in water. It may there- 

 fore be interesting if I record that I found it in about six inches of water, 

 at the bottom of the great ditch which conveys the Croydon sewage 

 on to the estate before it flows over the land, and that during the seven 

 weeks that have since elapsed, it has lived and thriven in a bowl of 

 water with two minnows." 



