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SCIENCE-GOSSIP. 



CONDUCTED BY J. H. COOKE, F.L.S., F.G.S. 



To whom Notes, Articles and material relating to Microscopy, 

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

 to be sent, addressed "J. H. Cooke, Edlcstonc, Battenhall 

 Road, Worcester," 



" The American Monthly Microscopical 

 Journal." — The current issue contains, among 

 other matter, articles on " Making Transparent 

 Lantern Slides from Marine Specimens," " Micro- 

 scopic Inspection of Pork for Export " and 

 " Bacterial Diseases transmitted through Oysters." 



Bacteria on Bronze Implement. — Professor 

 Nicholson found recently at Lewes a bronze imple- 

 ment which had on its surface certain small 

 excrescences. On examination he found that each 

 of these formed a centre of oxidation of recent 

 appearance. He scraped off and examined the 

 material under a quarter and one-seventh inch 

 objective, discovering that the oxidation was due 

 to bacteria which swarmed in it. He asks for 

 similar observations and a method of sterilization. 



Preserving Algae. ■ — To preserve without 

 shrinking use Flemming's weaker solution to kill 

 and fix the specimen (10 c. c. of one per cent, 

 osmic acid, 10 c. c. of one per cent, acetic acid, 

 25 c. c. of one per cent, chromic acid, and 55 c.c. 

 of distilled water). Its use for from half-an-hour to 

 twenty-four hours will not injure delicate tissues. 

 Add 10 per cent, of glycerine, allowing each drop to 

 diffuse before adding more. This will prevent the 

 shrinking caused by diffusion currents if glycerine 

 is added too quickly. Add the glycerine till the 

 specimen is well covered, when the fixing solution 

 has evaporated from a watch glass in which they 

 are exposed for the purpose. Red algae retain 

 their colour almost perfectly, but green algae lose 

 more or less colour, although the chromotaphores 

 retain their shape perfectly and the cells become 

 clearer than in fresh material. 



Acetylene in Microscopy. — We have for some 

 weeks past been experimenting with acetylene as 

 an illuminant in microscopy and have found it to 

 be an unqualified success. The light is so piercing 

 and intense that even after being modified by the 

 coloured glasses it reveals structures that are 

 invisible by the naked oil flame. Some timely 

 investigations in connection with this gas have 

 recently been made by Professor Lewis. The 

 phosphoretted hydrogen existing in the gas from 

 commercial calcium carbide ranges in proportion 

 from -6 to 2'oo per cent., but as experiment shows 

 that a percentage of 8000 is necessary to form a 

 mixture liable to spontaneous ignition, there can 

 be absolutely no danger from this impurity. In 

 one of the three types of generator now used, the 

 temperature rose above 8oo° C. in thirteen minutes. 

 At this high temperature benzine and tarry 

 matters are produced, reducing the volume of 

 liberated gas, and the type of generator is therefore 

 recommended in which the carbide is allowed to 

 fall at intervals upon a perforated tray submerged 

 in a large volume of water. 



Reproduction of the Rotifera. — The current 

 issue of " Natural Science " contains an interesting 

 article by Mr. W. T. Caiman on " The Progress of 

 Research on the Reproduction of the Rotifera," in 

 the course of which the various theories as to what 

 are the determining factors in evolution of sex are 

 reviewed. 



Mucilage for Labels. — Gumarabic, 150 parts, 

 tragacanth (pulverized), 7-5, glycerine, 450, thymol, 

 03, alcohol, 375, water up to i20'o. Dissolve the 

 gum arabic in 15 parts water, and the tragacanth 

 rubbed up with 30 parts water. Mix the two fluids 

 and strain. Next add the glycerine, and finally the 

 thymol dissolved in alcohol. 



Double Colour Illumination. — It is possible, 

 with substage condenser and iris diaphragm, to so 

 light a diatom as to reveal the primary structure 

 in one colour and the secondary in another. 

 Heretofore workers have used cones of light greatly 

 exceeding the aperture of the objective, or else 

 cones very much smaller than the aperture of the 

 objective. The former was on the dark ground 

 principle, the latter involved diffraction. The 

 "Microscopical Journal" now informs us that 

 Mr. Rheinberg has found a plan for getting rid 

 largely of diffraction colour effects, and for using 

 any cone of illumination desired. Just as in low- 

 power colour illumination on the dark ground 

 principle, he places in the substage condenser one 

 of the ordinary double-colour discs having a central 

 spot of one colour surrounded by a ring of a 

 strongly contrasted or complementary colour. He 

 prefers a red centre and a green periphery. By 

 means of the iris diaphragm, the relative pro- 

 portions of the two colours are so regulated that 

 in looking through the lenses the light appears to 

 be of a neutral tint. This arrangement is suitable 

 for use with high-power objectives. 



Microbes of London's Water. — In Sir E. 

 Frankland's annual report on London's water, just 

 published by the Local Government Board, some 

 very curious details may be found regarding the 

 extreme variability of the filtered product which 

 is supplied to water consumers in the metropolis. 

 Take for example the West Middlesex, which 

 month after month supplies its customers with 

 water of a high degree of purity, containing on one 

 occasion only four microbes per cubic centimetre, 

 and on another appearing to be absolutely sterile. 

 Of what advantage, however, is this, if on another 

 occasion the number amounts up to 120, and on 

 still another to 576 microbes per cubic centimetre ? 

 Something happened in the month of June to 

 nearly all of the filters of the five companies 

 drawing from the Thames ; all except the Southwark 

 were smitten with a microbial epidemic in June, 

 and even the Southwark had got it on the 2nd of 

 the following month. Of the two companies 

 drawing from the Lea, the New River alone 

 escaped. So serious was the condition that, from 

 the tables given to show the reduction of micro- 

 organisms by filtration alone, we find that in one 

 case 663 per cent, of the microbes passed the 

 filters. From all of this Sir E. Frankland points a 

 moral, and draws the attention of the companies to 

 the enormous advantage of fine sand in securing 

 efficient filtration. Some companies go to the 

 trouble of using much finer sand than others, with 

 apparently good results. Thus 18 feet of the fine 

 sand of the New River Company and 275 feet of 

 that of the West Middlesex are respectively more 

 than twice as efficient as 4 feet of the coarser 

 material used by the Chelsea Company. 



