HARD WICKE'S S CIENCE - G OS SIP. 



87 



of which a piece oi fine muslin is stretched, and con- 

 fined in a similar way. Arriving at the pond-side, 

 or at the seashore, or while the net is doAvn in tow- 

 ing, the collector snaps the band B around the mouth 

 of a glass tumbler, a jam-pot, beaker, or wide- 

 mouthed bottle, and proceeds at once to ladle water 

 in at c, which, finding its way into the containing 



Fig. 81. Pond-side Filter. 



vessel, rises through the finer muslin at d, and flows 

 off by the indiarubber tube E, the siphon-like charac- 

 ter of the arrangement materially assisting the opera- 

 tion, wiiile Desmids, Volvoces, Daphnia, Rotifers, 

 Floscularia, &c., are all retained in the three or four 

 ounces of fluid which the jam-pot or tumbler may 

 contain. Jennings' patent covers may be obtained at 

 the price of a few pence at either of the indiarubber- 

 shops in Ludgate-hill, or at Abbott Anderson's, in 

 Queen Victoria-street. — IV. Lane Scar, Margate. 



New Method of Illumination. — Being in 

 New Orleans some three weeks ago, and having some 

 curiosity to see the silver microscope made and ex- 

 hibited at the Royal Microscopical Society by Smith 

 & Beck about two years ago, I called on the owner. 

 Dr. A. W. Smyth, and ■\\'as very much pleased with 



the construction and working of the instrument, but 

 particularly with the effects produced by a mode of 

 illumination which was claimed by him as original 

 and exceedingly simple. It was produced by a disc 

 of ordinary cover-glass ground on botk sides, and 

 used in the same place and in the same manner as 

 the ordinary black-ground stop below the condenser, 

 the marginal rays of light passing unobstructedly 

 around the outer edge of the ground cover-glass, 

 producing a difterent and far more pleasing effect 

 than that produced by the ground glass extending 

 over the whole aperture of the condenser, and en- 

 tirely different to that produced by a ground glass 

 cap over the top of the condenser. I am sure your 

 readers will be pleased with this simple mode of 

 illumination on nearly all objects usually viewed on 

 black ground, as well as those objects viewed by 

 direct light. — jf. A. Perry. 



Bramhall's Horizontal Super or Sub-stage 

 Reflector. — Mr. Bramhall's recommendation of 

 this, backed by the authority of Mr. F. Kitton, in- 

 duced me to order it. Some delay occurring in its 

 receipt, probably owing to accidental circumstances, 

 I resolved to make a temporary substitute, and, with 

 this view only; disregarding the precise instructions 

 given in Science-Gossip (p. 136, 1876), chose ma- 

 terials that came most readily to hand and promised 

 least trouble to adopt. A small toy mirror-plate, a 

 cardboard back and millboard front of the same size, 

 the latter punched centrally with a |-in. aperture; 

 two pieces of gummed covering-paper, that for the 

 upper side being similarly perforated ; in a few 

 minutes, I provided an accessor)' which enabled me to 

 see the transverse markings on A. pellucida under 

 ~ immersion with eye-piece and 3-in. draw-tube. 

 The conditions of stand, stage, and light being all 

 unfavourable, and purposely accepted to severely test 

 asserted fitness to supply students and others with a 

 substitute for costly appliances which will always be 

 used by those who can affoixl such luxuries. This 

 result and others, obtained with a low angle 5th (blue 

 glass being interposed between condenser and the 

 slide lying upon it), surprised me ; the latter were 

 very beautiful, and not less wonderful, as I think, the 

 fine lines of S. gemma being distinctly visible, and 

 those on more difficult valves dimly so. A stereo- 

 scopic image of P. dngidatitm and balticnin gave a 

 better idea of their shape and character than I had 

 ever before got. Mr. Kitten's praise would seem, as 

 might be expected, to be well deserved, and pro- 

 bably both my mechanical execution and manipula- 

 tion are open to improvement by longer acquaintance 

 with this inexpensive condenser. — M. O. H. 



Mounting in Dajiar. — I am very glad to see 

 that, at last, the use of damar as a mounting medium 

 is so warmly advocated, especially in the extremely 

 convenient form mentioned — namely, in a tube : 

 nothing could be cleaner, nothing more expeditious; 



