HARDWICKE'S SCIENCE-GOSSIP. 



39 



so that the large may be separated from the smaller 

 kinds. Before sifting, however (indeed, before I have 

 entirely freed them from the sand, &c.), I boil them 

 for some few minutes in water to which has been 

 added a small quantity of liquor potassiF—%z.y a table- 

 spoonful in a quart of water — if too strong it will 

 disintegrate the shells. Allowing time for the sub- 

 sidence of the minutest forms, I carefully pour off 

 the discoloured water, and add a fresh portion, repeat- 

 ing the process until the water comes off perfectly 

 clear, when the residue may be thoroughly dried in an 

 oven. 



A little of this white powder at a time may then 

 be thrown into a glass vessel of water, the lighter 

 forms of Foraminifera will float, and may be collected 

 with a feather, the bulk of the material will have sub- 

 sided, and, after pouring off the water, it must again 

 be dried, and the process again and again repeated, 

 until none but the heaviest forms sink with the sand ; 

 these also may be gathered by stirring the contents 

 of the vessel, and after allowing the solid particles to 

 subside pouring off the water without disturbing the 

 sediment, which should be gently skimmed, the 

 skimmings set aside, and this process, also, again and 

 again repeated, until foraminifera almost entirely free 

 from foreign matter are ultimately obtained. The 

 whole process is a most tedious one, but, if properly 

 performed, the result will be in every way satis- 

 factory. I recently prepared about thirty pounds of 

 this "sponge sand," obtaining as the fruit of my 

 patient labour about — "Two or three pounds of Fora- 

 minifera ! " perhaps some eager microscopist will 

 exclaim. Nay, not so ; but about a piled-up tea- 

 spoonful of exquisite shells, the gathering consisting 

 of a very large proportion of all the known forms. 

 Fig. 22 exhibits a small portion of a slide of medium 

 sized shells, viewed as transparent objects with a 

 two-inch objective. Higher powers, of course, may be 

 employed with advantage. 



After mounting some hundred or so slides for ex- 

 change, I was still able to supply my micro-friends 

 with unmounted material. 



Although a series of slides would exhibit many of 

 the rarest forms, no single mount will do so, even 

 though it may contain many hundreds, or even 

 thousands, as mine do. I therefore keep in my col- 

 lection not less than a score of slides, some exhibiting 

 rare forms that do not occur in others. 



When preserved by the microscopist for examina- 

 tion as beautiful objects, I consider that no method of 

 mounting surpasses that of immersion in Canada 

 balsam, since, if properly prepared, the structure of 

 the shell, the foramina, the septa or divisions of the 

 chambers, are all made distinctly visible, and they 

 can still be viewed as opaque objects if the light be 

 concentrated upon them, when they present an ex- 

 quisitely opalescent appearance. Deep cells contain- 

 ing a quantity of the loose material may also be added 

 to the cabinet. 



For scientific examination it will be necessary to 

 view them under every possible condition and mode 

 of illumination and preparation, in order to arrive at 

 a due conception of their form, and the disposition of 

 the openings ; and a student will, doubtless, find it 

 necessary to isolate the various forms for this purpose 

 — a tedious process, but one that will well reward his 

 patience. 



Great care is requisite in preparing these tiny shells 

 for their final "mount," since the several chambers- 

 often most obstinately, for a length of time, resist 

 every attempt to dislodge the included air. Most 

 persons will consider air bubbles a great disfigurement, 

 and the preparer should invariably expel the whole of 

 them before offering his duplicates for exchange. 



Once mounted, I class them according to their size, 

 usually numbering from i to 6. No. i contains the 

 largest forms. No. 6 the smallest. 



The fossil forms from the chalk may be obtained by 

 repeated washings, and I venture to think that the 

 method suggested by myself in Science-Gossip, in 

 February, 1867, will yield the microscopist as fair a 

 result as any with which I am acquainted. 



Davies on Mounting Micro-objects describes other 

 methods, which some may prefer. 



These shells commonly occur in the flints of the 

 chalk formation, and those curious bodies the 

 Coscinopora, once believed to be small sponges, are 

 now classed by Dr. Carpenter amongst the Foramini- 

 fera. Polished sections of flint often exhibit ver>^ 

 beautiful forms. The figures which illustrate this 

 paper will convey a far better notion of the varied 

 forms of these beautiful organisms than any written 

 description would do. 



NOTES ON NEW BOOKS. 



T^OSSILS OF THE BRITISH ISLANDS 

 ± Stratigraphically and Zoologically Arranged, 

 by Robert Etheridge, F.R.S., &c. (Oxford : The 

 Clarendon Press). Many years ago, the late Professor 

 Morris brought out a "Catalogue of British Fossils," 

 which proved of great service to geologists. But 

 the present work is based on a much more extensive 

 scale. The volume before us deals only with the 

 fossils of the Palxozoic formations. Nevertheless, it 

 runs to 468 pp. quarto of closely-printed matter. It 

 is indeed a gigantic labour, and one which no other 

 man than Mr, Etheridge would have found either 

 the knowledge or the patience to have given to it. 

 In his long and useful position as Palaeontologist to 

 the Geological Survey, he doubtless had opportunities 

 for dealing with a work of the present description 

 possessed by no other man. Some idea of the labour 

 involved may, be gathered from the fact, that it has 

 been in hand the last twenty-four years. 1,588 

 genera, and 6,200 species of fossils are described, 

 ranging from the Cambrian to the Permian forma- 



