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HARDWICKE'S SCIENCE-GOSSIP. 



[June 1, 1867. 



to preserve its hardness and brittleness, for that on 

 tlie specimen in question is extremely hard, and as 

 sharp at the edges as at first. In the other case 

 the object was mounted in a cell ground out of 

 the glass, and the thin glass cover cemented with 

 black asphalte cement, which also has stood re- 

 markably well, though, as it was laid on in a very 

 narrow band, a large globule of air has got in, which 

 spoils the appearance of the slide as a mounted 

 specimen, but has not aifected the object in the least 

 degree. Distilled water, having thus stood the 

 test of eighteen years, is, I think, shown to be a 

 suitable fluid for, at least, vegetable tissues. 



While on the subject of fluids and cements, I 

 may take the opportunity of stating that marine 

 glue (which answers so admirably for fastening 

 glass rings to slides) when kept in the lump, loses 

 its properties after two or three years in a hot 

 country. When strips of it are laid on a slide and 

 held over a spirit lamp, or if a piece of it be held in 

 the flame, instead of melting, it bums and smoulders 

 away into a dry ash, and is therefore useless. It is 

 the same, also, with ordinary English sealing-wax, 

 so that it is impossible to seal a letter with it.— 

 C. S. P. P., Mouhnein. 



Eatty Acids.— E. Histed speaks of spermaceti 

 as a good polariscopic object : I, to the same effect, 

 recommend the fatty acids, either by E. H.'s process 

 or otherwise in the ordinary way. — S. D. 



Movements oe Diatoms. —Science-Gossip is, 

 I apprehend, a publication in which I may quietly 

 buttonhole your own proper person, and relate what 

 I have seen recently in our instrument of instru- 

 ments, the microscope. Now, although I possess a 

 few books relating more or less to all subjects which 

 come under the said instrument's glass eyes, I am . 

 not aware of any which clear up the question of 

 "How do the navicular force their way through 

 the water ? " Neither do I for one moment suppose 

 that a humble individual like myself is going at 

 once to solve it. I shall, however, relate (if you 

 will kindly lend your ear) what I have lately seen. 

 After a trip last Saturday, May 11th, to Swanscombc, 

 which somehow or other is not now what Swans- 

 combe was formerly (speaking from a microscopic 

 point of view), I found that I had got Surirella, 

 P. angulata, Nitzschia, P. elongata, P. fasciola, 

 P. quadrata, Amphiplura, &c., &c, not to mention 

 any quautity of ciliated and non-ciliated animalcules. 

 With regard to the means of viewing them, I con- 

 sidered my Poss compressorium the best, and conse- 

 quently transferred from my soup-plate (into which 

 all the gatherings had been as usual turned) a drop 

 from the surface. Eor the first time in my life I 

 found a quadrat urn on edge— not having, as in ninety- 

 nine cases out of a hundred, screwed down the top 



glass until all underneath must be flat — which gave it 

 a curious appearance. In the ordinary mode of 

 seeing these minute objects, there appears when 

 alive, as every one has seen, a central spot, and 

 a minute ring at either extremity. Our friend 

 viewed sideways, gave me apparently the idea 

 that the two rings might be the orifices of two 

 tubes, and it struck me that the Puthven pro- 

 peller, in which water is sucked in at one end of the 

 vessel and ejected at the other, might really be the 

 principle upon which our Pleurosigma get along. 

 If this is anything very old, let your humble servant 

 down as lightly as possible. I mention it purely as 

 gossip. 1 saw no motion, but I think my specimen 

 was defunct. Does the central ring exercise any 

 influence upon the two tubes in contracting and 

 expelling the fluid, or otherwise ? The powers used 

 were a good ^ and £. The y would not go through 

 the thickness of glass and water necessary to keep 

 the object in position. I bring this forward simply 

 because it is likely some of your readers may have 

 seen the same sort of thing, and at the same time, 

 with that feeling of diffidence that makes those who 

 work long at the microscope not always to believe 

 their own eyes. — John Bockeit. 



Glenshira Sand.— In answer to J. W. W.'s 

 inquiry respecting the method employed by the 

 late Dr. Gregory with Glenshira sand, I have 

 pleasure in informing him that, in a letter written 

 by the Professor to an acquaintance of mine, he 

 directed him to have four or six glasses, each about 

 twelve inches high ; into the first, nearly filled with 

 water, to pour some of the sand, and to allow it 

 one minute to settle, the fluid to be then carefully 

 poured into the second glass, and two minutes to 

 be allowed previous to the fluid being decanted 

 from the deposit into the third glass, and here 

 four or five minutes were to be allowed ; the process 

 to be thus repeated, doubling the time for the 

 sediment to settle in each glass; the deposit will 

 consist almost entirely of sand in the first glass, in 

 the next of sand and the larger diatoms, the finest 

 kinds being found in the last glasses. 



If J. W. W. is desirous of exchanging Glenshira 

 sand for other diatomaceous material, the writer 

 will be glad to hear from him. — Joseph B. Bod man, 

 Castor, Peterborough. 



Mounting Diatoms.— How must I proceed in 

 order to make diatoms stick on the slides after they 

 are arranged ? 1 have succeeded in arranging small 

 groups, but all trials to make them stick have been 

 in vain; the diatoms float away as soon as the 

 balsam is put on them, and yet it is possible to fix 

 them, as is proved by the beautiful preparations 

 which are sold in England. — E. W. Schoenebcck, 

 Prussia. 



