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HARDWICKE'S SCIENCE- GO S SIP. 



[Oct 1, 1S67. 



MICROSCOPY. 



Apparatus tor Drawing Objects. — I have read 

 several suggestions in Science-Gossip upon micro- 

 scopical drawings, but have not seen mentioned a 

 very simple method I have tried, and which any 

 person with a little ingenuity could manage easily. 

 Having myself done'a deal of microscopical drawing, 

 I can answer for the plan I describe below. Get a 



Polarizing Object.— One of the most beautiful 

 objects under the polariscope with which I am 

 acquainted is the fresh-water shrimp, which may be 

 found in any stream. — Samuel Morris. 



Phyllactidium.— In an interesting article on 

 Phyllactidium in the August number of your perio- 

 dical, there is an intimation to the effect that you 

 will be glad to record any additional localities where 

 that beautiful water-weed has been found. I have 



™^ 



Fig. 249. Apparatus for Drawing. 



common deal muscatelle box at any grocer's shop, 

 cut a hole in one end large enough to fit the body 

 of the microscope ; the wood from the opposite end 

 of the box should be taken entirely away, and in its 

 place fitted a sheet of common window glass. Then 

 place the microscope in a horizontal position, insert- 

 ing the eye-piece end of the body into the hole made 

 for it in the box (the eye-piece is not used), then 

 with a bull's-eye condenser concentrate direct rays 

 of light from a lamp through the object, which can 

 now be focussed, in the same way as the magic- 

 lantern, on to a sheet of paper which is placed over 

 the glass for drawing. With a 1 or 2-inch object- 

 glass, very excellent outline drawings can be made. 

 The above figure (fig. 249) will immediately ex- 

 plain its simplicity. — John Robins, Bartholomew 

 Close. 



The Chalk. — Searching the chalk for forami- 

 nifera, a diatom is occasionally found, and by dissolv- 

 ing the chalk in dilute nitric acid, and afterwards 

 boiling the residuum in strong acid, as with other 

 infusorial earths, a variety of spongispicules and 

 diatoms may be obtained. These are, indeed, few 

 and far between as compared with those of the rich 

 Toome Bridge earth, and yet the same forms are 

 found in both, with one or two exceptions. The beau- 

 tiful little circular discs with fine markings are con- 

 spicious iu both. Chalk being a marine deposit, it 

 would appear that the Toome Bridge earth is so 

 likewise, and that the country bordering the river 

 Bann, where it is found, has been covered with salt 

 water since the formation of the peat mentioned in 

 Mr. Gray's interesting paper. I find no diatoms in 

 the lower chalk from Folkestone ; in the upper 

 chalk here they are frequent, though not abundant. 

 — S. S., Brighton. 



noticed the plant in question adhering in great 

 numbers to the sides of an aquarium which I esta- 

 blished iu 1S62, the material of which I got from 

 ponds in the neighbourhood. Last year I had an 

 accident with it in the shape of a breakage. I set up 

 another soon after, but hitherto I have not seen a 

 single specimen of Phyllactidium ; it seems to have 

 given place to that beautiful polyp the Hydra viridis. 

 ■ — Samuel Morris, Casterton, Kirkby Lonsdale, West- 

 moreland. 



Foraminifera. — (Reply to J. H. G.) — The 

 object of washing the pounded chalk is entirely to 

 remove all traces of it from the fossils ; the washing 

 must therefore be continued until this result be ob- 

 tained ; whether in one washing or several must of 

 course depend upon the length of time allowed, the 

 nature of the chalk used, and the expertness of the 

 operator. Some chalk, particularly the lower, con- 

 tains no fossils whatever, whilst other samples, as the 

 Kentish, say from Gravesend, Charlton, &c, abound 

 with them — as a rule, that containing many large 

 fossils will be found rich in foraminifera. It is better, 

 before operating on a piece, to wash the surface with 

 a brush under a stream of water; if upon viewing it 

 with a magnifying glass, no minute shells are visible, 

 it will probably yield few when prepared, and vice 

 versa. The milky fluid should not be thrown away, 

 but carefully washed, as it contains the most minute 

 fossils. J. II. G. perhaps washes his chalk too little, 

 instead of too much, and should try another piece ; 

 unless well washed, the particles of chalk adhere so 

 tenaciously to the fossils that their form is not easily 

 discerned. The masses alluded toare probably pieces 

 of the tests of echini, &c, and the pencil species 

 of spatangi. The fossils must either be viewed 

 as opaque objects — dry, or mounted in balsam, if 

 as transparent objects. — Edward H. Robertson.) 



