66 



HARDWICKE'S SCIENCE-GOSSIP. 



We learn the Philadelphia Academy of Sciences is 

 building up a very fine herbarium, claiming to 

 possess probably one-half the known species of 

 plants. The growth has been very rapid for some 

 years, the past year showing an addition of 2,868 

 species. The species are all poisoned, labelled, and 

 systematically arranged, and this great work is being 

 done gratuitously, by the persistent labours of Mr. 

 J. H. Redfield, assisted by other botanists. 



Dr. H. W. Crosskey's paper in the Birmingham 

 Philosophical Society's Proceedings, on " The 

 Grooved Blocks and Boulder-clays of Rowley Hill," 

 and on other unmarked boulders, is accompanied 

 by some of the most beautiful lithographs we have 

 seen illustrating scientific papers. Dr. Crosskey gives 

 sketches of ice-marked boulders from Switzerland, 

 to illustrate those from the above neighbourhood. 



The storm of Saturday night, January 26th, was, 

 for the short time it lasted, one of the most violent 

 experienced for some time. The wind-pressure in 

 the north-east of Scotland was for a few seconds, 

 thirty-five pounds on the square foot. The barometer 

 settled to a little over twenty-seven degrees, and the 

 difference in barometrical pressure between Scotland 

 and France at the same time was two inches. 



MICROSCOPY. 



On Gum Styrax as a Medium for Mounting 

 Diatoms.— In the "Bulletin de la Soc. Beige de 

 Microscopic," No. ix., 1883, Dr. Henri Van-Heurck 

 describes two resins he had discovered in his search 

 for a fluid to take the place of monobromide of naph- 

 thaline'; this medium, in spite of its high refractive 

 index (i"65), is on account of the difficulty of per- 

 manently securing it in the cell, and its disagreeable 

 odour, but rarely employed. The two resins are the 

 products of Liqiddanibar orieiitale and Z. styracijlua ; 

 the former plant grows in Syria, the latter in North 

 America. The resin yielded by the Syrian plant is 

 prescribed in the British Pharmacopoeia under the 

 name of Gum Styrax, and in the drug trade is known 

 as " strained gum styrax." It has the colour of the 

 old-fashioned black treacle, but is of greater con- 

 sistency ; a temperature of 212° renders it fluid. In 

 its commercial state it is unfit for microscopic 

 purposes, first from its impurities (probably owing to 

 the rough method employed in obtaining it; the 

 stems are cut in small pieces and boiled, when the 

 gum rises to the surface and is skimmed off), and 

 second, from its thickness. It is therefore necessary 

 that it should be dissolved in one of the followino- 

 menstrua : chloroform, benzoic, ether, a mixture 

 of benzole and absolute alcohol. When the resin is 

 dissolved it must be filtered, and it is then ready for 

 use ; the solution should be of the colour of brown 



sherry, and the consistency of limpid olive oil. Its 

 consistency can of course be increased by evaporating 

 a portion of the benzole, and the whole of the latter 

 should be eliminated before placing the cover on the 

 slip ; its refractive index is then 1*63, very nearly 

 that of monobromide of naphthaline. The American 

 liquid-amber is prescribed in the American " Phar- 

 macopoeia," but seems to be unknown in Europe. It 

 would, if obtainable, be preferable to gum styrax, as 

 its colour is a pale yellow. The colour of the styrax 

 is practically of little consequence, as the film 

 between the cover and sl'p is very thin, and does not 

 show any appreciable amount of colour when placed 

 under the microscope. I have, during the past four 

 or five months, used this medium for various 

 diatomaceze ; among others Vanhenrkia rhomboides, 

 Amphipleura Lindheimeri, Pleurosigma angulatum, 

 P. littoralc, Naviciila cuspidata ; the transverse stride 

 on P. Httorale, and the longitudinal on N. cuspidata, 

 are much more sharply defined, and the striae on all 

 of them are more easily resolved than when mounted 

 in Canada balsam. The most striking difference 

 between gum styrax and Canada balsam is displayed 

 by Polymyxus ioronalis ; in balsam the valves are 

 perfectly hyaline, and the rays and puncta almost 

 invisible ; in gum styrax the valves are light brown, 

 and the markings easily resolved. Heliopelta, as 

 might be expected, does not exhibit more structural 

 detail, but every line and dot are more distinct than 

 when it is balsam mounted. Several of the Aulisci 

 are also much improved when mounted in this 

 medium. I cannot say much of its merits as a 

 medium for mounting other microscopic objects. I 

 have tried it for thin wood-sections, hairs, chalk 

 foraminifera, and a few butterfly scales, all of which 

 show better than they do in balsam. The colour of 

 styrax becomes objectionable when a thick layer is 

 necessary. Dr. Van Heurck directs that the com- 

 mercial gum styrax should be exposed in thin layers 

 to the light and air for several weeks, to eliminate the 

 moisture contained in it previous to dissolving it. I 

 have not found this necessary with my sample. The 

 gum storax, one of the ingredients of incense, is 

 useless. — Fred. Kittoit, Hon. F.R.M.S. 



Preservation of Protozoa and Small Larv^. 

 — Hermann Fol recommends an alcoholic solution of 

 ferric perchloride to kill small animals without injury 

 to the tissues. It is diluted with water down to two 

 per cent, and then poured into the vessel holding the 

 animals. These then sink to the bottom. The water 

 is poured off, and seventy per cent, alcohol substituted. 

 Change the alcohol and add to the second dose of it 

 a few drops of sulphuric acid ; otherwise the iron 

 may remain in the tissues, and cause them to over- 

 stain with colouring reagents. The alcoholic washing 

 should be thorough. Even larger animals (medusae, 

 dolium, &c.)J may be perfectly, preserved by this 

 method. The tissues may be subsequently stained 



