HARDAVICKE'S SCIENCE-GOSSIP. 



17 



over the faucet of the hydrant in the evening-, and 

 allow a small stream of water to puss through it all 

 night. In the morning take off the muslin and rinse 

 in a little water." The above plan, if tiied in this 

 country, would probably supply some of the fresh- 

 water forms, as Asteiionella, Dluior.ut, Sijnedra, &c., 

 in tolerable plenty ; but 1 fear the experimenter 

 would be liable to an action from the water com- 

 pany for waste ! 



"Woody Structuee eeplaced by Puue Silver. 

 — It is suggested that interesting metallic casts, 

 sliowiug the structure of wood, might be made by 

 taking advantage of the deflagration of nitrate of 

 silver on charcoal. When a crystal of nitrate of 

 silver is placed on a piece of burning charcoal, it 

 fuses and sinks into the pores of the wood ; and 

 as each atom of charcoal is replaced by one of silver, 

 the structure of the wood is preserved. The modus 

 operandi is thus described by Dr. Chandler :—" A 

 crystal of nitrate is placed on a piece of charcoal, 

 and a blowpipe flame directed upon the coal near 

 to the crystal, to start the reaction. When defla- 

 gration commences, crystal alter crystal may be 

 added ; the nitrate fuses and passes down through 

 the porous metal, already reduced, until it reaches 

 the burning coal, where it is reduced." Lumps of 

 silver, weighing an ounce or more, exhibiting the 

 rings of wood in a most beautiful manner, have been 

 thus prepared. 



The ANniAL Nature oe the Spongiad^. — 

 Vix. H. Carter sends the following connnunieation 

 to SUlluutn's Journal, in which he says : " You 

 will be glad to learn that I have couflrmed all that 

 Prof. J. Clark, of Boston, has stated about the 

 tponge, and more too, confirmed by an examination 

 of a marine calcareous sponge, I have not only fed 

 the sponge with indigo, and examined all at the 

 same moment, but the sponge so fed was put into 

 spirit directly afterwards, and now shows all the 

 cells (mouociliated) witii the ciliiim attached, and 

 the indigo still in the cells." 



Arborescent Silver.— The very beautiful slides 

 knowu to most microscopists under the above title 

 are very -easily produced, and as every preparation 

 almost invariably shows some striking variation, 

 some of the readers of Science-Gossip may be de- 

 sirous of knowing the modus operandi. A drop of a 

 very weak solution of nitrate of silver is placed on 

 the centre of a slide, a small piece of tl)e finest 

 copper wire is then laid in the middle of the drop ; 

 crystallization at once commences, and when it has 

 proceeded as far as the operator desires, the remain, 

 ing nitrates of silver and copper must be poured off : 

 this requires careful management. The best plan 

 is to breathe on the slide, and then gently tilt it on 

 one side : this causes the fluid to drain away from 

 the crystals. A little distilled water must then be 

 allowed to flow from the opposite side : this will 



wash away the nitrate of copper, and the slide will 

 dry, and remain so, A small quantity of gum mixed 

 with the distilled water will retain the crystals in 

 their place (about three drops of the ordinary solu- 

 tion of gum in half an ounce of water is suflicient). 

 The slide may now be dried and mounted in an 

 asphalte cell. However, before doing so, itr is better 

 to remove the copper wire. This is best done by 

 gently pushing one end of it: this will detach the 

 crystals, and it can then be taken up by the aid of 

 a small pair of forceps. — F, K. 



GEOLOGY. 



At a recent meeting of the New York Lyceum of 

 Natural History, Professor A. M. Edwards showed 

 that the substance called "guano," used in the 

 manufacture of artificial manures, is not, as is 

 usually supposed, the accumulated droppings of 

 birds, but a mud formed by the accumulation of the 

 bodies of animals and plants, for the most part 

 minute, and belonging to the group which Haeckel 

 has collected into a new kingdom under the name 

 oi Protista. It was deposited along the ocean-floor, 

 and eventually upheaved to the elevations in which 

 its strata are now found. Subsequent changes so 

 altered it that the organic matter was transformed 

 to bitumen. The diatomaer fe, &c., found in guano 

 occur as they would present themselves if deposited 

 in water, and not as they would if they had passed 

 through the stomachs of fish and birds. 



Ix the December number of the Geological Maga- 

 zine, Mr. AVilliam Carruthers, F.R.S. (of the Britisii 

 Museum), has figured and described two new 

 species of fossil coniferous fruits from the gault- 

 beds of Eolkstone. He states one species to be 

 allied to the existing IFellingtonia, and shows that 

 they point to the existence of a coniferous vegeta- 

 tion on the high lands of the Upper Cretaceous 

 period, which had a fades similar to that now 

 existing on the mountains on the west of North 

 America, between the tiiirtielh and fortieth paral- 

 lels of latitude. No fossil referable to Sequoia has 

 hitherto been foup.d in strata older than the Gault, 

 and here, on the first appearance of the genus, we 

 find it is associated with pines of the same group 

 that now flourish by its side in the New World. 



Dr. Duncan, E.R.S., has recently shown that a 

 peculiar coral {Canjophyllia cylindracea), which has 

 hitherto been regarded as peculiar, in the fossil 

 condition, to the upper chalk strata, still lives in 

 the deep-sea regions of Havannah, and off the I beriau 

 peninsula. It belongs to the group possessing only 

 four cycles of septa in six systems. 



A USEFUL ADDITION to our coal supplies has been 

 made by the discovery, at Halesowen, near Bir- 

 mingham, of a seam of coal fourteen feet thick- 

 This fact controverts the theories .hitherto held as 



