SCIENCE-GOSSIP. 



269 



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1ICR05C0PY 





CONDUCTED BY 



H. COOKE, F.L.S., F.G.S. 



Tosh- -. rial relating to Microscopy, 



and intended for Science-Gossip, are, in the first instance, to 



be s. .:■• J. H.Cooke, Thomdale, Lincoln." 



Microscopical Preparations. — We are in 

 receipt of a copy of the " Revised Catalogue of 

 scopical Slides, etc., 1S97." issued by Mr. 

 R. Suter, of South Tottenham, Middlesex. It con- 

 tains some useful detailed lists of mounting 

 materials and naturalists' requisites. 



A Minute Flowering Plant.— The smallest 



flowering plant yet discovered is the Wolfia 



.".sis, of the Duckweed family, which appears 



on stagnant pools as a green ball, a thirteenth of 



an inch in diameter. 



Ross' Industrial Microscope. — The great 

 utility of microscopical research to purposes of 

 advanced agriculture is now so fully recognized 

 that the recent demand for a less costly instrument 

 than those usually supplied has induced Messrs. 

 Ross and Co. to design, for the use of farmers, 

 manufacturers in the textile trades, and students, a 

 microscope which, while combining efficiency with 

 stability, is free from any unnecessary complica- 

 tion. Those who may require such an instrument 

 at a most reasonable price, should see Ross' New 

 " Industrial " Microscope. 



Microstereograms. — Many methods for the 

 production of microstereograms of microscopic 

 objects have been proposed, all of which are more 

 or less practicable with low-power objectives. 

 Dr Gebhardt. in " Photographische Rundschau," 

 describes yet another which enables the operator to 

 produce photographic stereograms with high-power 

 objectives. The effects are strikingly steroscopic, 

 and. as no special appliances are required beyond 

 the ordinary Abbe condenser, anyone possessing 

 a moderately equipped microscope and a camera 

 can try the experiment for himself. Two exposures 

 are made, the lighting being so arranged that the 

 object is first illuminated on one side and after- 

 wards on the other. By this method, something 

 equivalent to an optical shading of half the objec- 

 tive is realized, the result of which is an appearance 

 of solidity in the object that is most striking. 



tallization op Salts.— The following 

 method of preparing salt crystals on glass slides 

 for use with the micro-polariscope is simple, 

 ■ live hither of the following 

 salts: barium nitrate, potassium chlorate or 

 oxalate, sodium oxalate or nitrate, zinc or copper 

 acetate, microcosmic salt or iron sulphate, may be 

 dissolved in hot water to make saturated solutions ; 

 benzoic acid or pthalic.v Insoluble in water, 



must be dissolved in alcohol. Having carefully 

 cleaned the glass slide, apply a little of 1)1': solution 

 to it a- with a tumbler 



1st settling on it The addition of a 



>(ar to the solution tends to fix the crystals to 

 to make lantern slides, 

 the salt* should br (water, 



In this ca.se. the sugar may be dispensed with 



Cutting Sections of Lignite. — The intense 

 blackness of lignite is a serious obstacle to a 

 satisfactory microscopical examination. It is 

 most difficult to get a section by the ordinary 

 grinding processes that shall be thin enough to 

 allow of its structure being viewed by transmitted 

 light. Even when the section is so thin as to be 

 on the verge of breaking up, it is still too opaque 

 for the strongest light to pass through it. The 

 best method to adopt is that which is recommended 

 by Griffith and Henfrey for the examination of 

 coal. The specimen should be macerated for a 

 week or more in a strong solution of carbonate of 

 potash, at the end of which time it is possible to 

 cut tolerably thin slices with a razor. These slices 

 are then placed in a watch-glass with strong nitric 

 acid, covered, and gently heated ; they soon turn 

 brownish, then yellow, when the process must be 

 arrested by dropping the whole into cold water, or 

 else the specimen would be dissolved. The 

 slices thus treated appear of a darkish amber 

 colour, very transparent, and exhibit the structure, 

 where existing, most clearly. The specimens are 

 then carefully washed in pure water, and are best 

 examined in glycerine, and may be mounted 

 permanently in cells of that fluid. 



Haddonia. — This new genus of foraminifera, 

 Mr. F. Chapman explained at a recent meeting of 

 the Linnean Society, is a calcareo-arenaceous type, 

 of the sub-family Lituolinae (of Brady). The 

 species Haddon ia torrcsiensis is adherent tocoral-rock, 

 and resembles an attached and well-grown Haplo- 

 phragmium. The aperture is partially closed 

 by a flap or valve, sometimes directed towards, 

 sometimes away from, the attached surface of the 

 test. The specimens of H. torrcsiensis were found 

 in great abundance on two specimens of coral rock 

 collected by Professor A. C. Haddon, in the Torres 

 Straits, in 18S9. 



Parasitic Enemies of the House Fly. — The 

 house fly has a number of natural enemies, many 

 of which serve as interesting subjects for micro- 

 scopical investigation. In its larval stages it is 

 subject to the attacks of hymenopterous parasites 

 and of predatory beetles. In its adult condition 

 it is infested by a small reddish mite, which 

 frequently covers its body and gradually destroys 

 it. It is also killed in considerable numbers by 

 the common house centipede. Its most effective 

 enemy, however, is a fungus disease known as 

 Empusina muscat, which carries it off in great num- 

 bers, particularly towards the close of the season. 

 The epidemic ceases in winter, and although 

 enormous numbers are killed by it, the remarkable 

 rapidity of development in the early summer 

 months more than replaces the thousands thus 

 destroyed. 



Mounting Foraminifera. — Mr. E. Earland 

 recommends gum tragacanth as being the best 

 fixative medium for mounting foraminifera. It is 

 preferable to gum arabic as it becomes nearly 

 invisible when dry, and it is also less subject to the 

 influence of those changes in the weather which 

 often cause foraminifera mounted with gum arabic 

 to crack and break. Mr. Earland prepares his 

 mountant by partially dissolving the finest powdered 

 gum tragacanth in spirits of wine jusl BUffii lent i" 

 cover the powder. A small crystal of thymol 

 added to the spirit sterilizes and preserve, the 

 Ige (rom mould, after whii li Millie ienl 

 distilled '..iter li added to dilute it, till it becomes 

 a very thin jelly of such a consistency thai will not 

 run from the bottle when tilted. The gum 



