Feb. 1, 1867.] 



HAEDWICKE'S SCIENCE GOSSIP. 



43 



MICEOSCOPY. 



Polariscopic Objects. — I desire to direct at- 

 tention to a beautiful series of polariscopic objects 

 which may easily be obtained from prawns, and 

 possibly from shrimps and other crustaceans. Under- 

 neath the shell of these may be found, at certain 

 times, a very slight, incomplete, and fragmentary 

 deposit of crystals not much unlike the scales on 

 some fish. The crystals are of irregular forms and 

 various sizes, and are probably carbonate or oxalate 

 of bme, and when united they appear to form the 

 new shell of the prawn which is ready for use when 

 the older shell has been cast away. On mounting 

 the crystals or scales on balsam, and placing 

 them under a polariscope, they will be found to 

 exhibit the most beautiful iridescent colours ; and 

 so thoroughly and essentially polariscopic are the 

 crystals, t tkat even without a selenite plate their 

 colours are gorgeous. — T. P. Barkas, Neiccastle- 

 on-Tyne. 



Hardening Canada Balsam. — At the Decem- 

 ber meeting of the Quekett Microscopical Club, 

 during a discussion on this subject, Mr. Hislop 

 described the following simple and effective plan 

 which he had adopted with great success. He had 

 two plates of brass, 2} inches wide by 5 or 6 inches 

 long, and T V of an inch, thick, which were placed 

 on a tripod over a gas flame turned down to the 

 blue, so as to keep the plates hot enough to be 

 unpleasant to the hand. After mounting the 

 objects, he places the slides on the brass plates ; 

 and on taking them off again in an hour's time, he 

 finds the balsam in nine cases out of ten to be hard 

 enough to scrape off and finish. No difficulty is 

 found to arise from air-bubbles, and those which 

 form of themselves disappear as the balsam be- 

 comes hard. 



The Quekett Soiree. — The first soiree of the 

 Quekett Microscopical Club was held at University 

 College on the 4th of January, and, notwithstanding 

 the inclemency of the weather, about 400 persons 

 were present. Amongst the " attractions " of the 

 evening were Dr. Mary Walker, a living Stepliano- 

 ceros, Quekett's own microscope, and a curious 

 microscope exhibited by Mr. Burgess, which gave a 

 field of apparently eighteen inches. These divided 

 a lion's share of attention amongst them. A large 

 number of microscopes were exhibited by the mem- 

 bers, including the principal makers. 



Acari. — Any correspondents willing to aid in the 

 investigation of British Acari, with a view to the 

 publication of a work on the subject, are invited to 

 send specimens of mites, water-mites, or ticks, in- 

 closed in quills, addressed to "Acarus," care of the 

 Editor, 192, Piccadilly, London, W. 



Asphalt Cement. — The number of commu- 

 nications you have on the subject of making asphalt 

 cement from Mr. Davies's receipt, shows that many 

 fail in their attempts to dissolve, the asphaltum iu 

 naphtha, and are driven to other expedients, such 

 as dissolving it iu benzoli, turpentine, &c. Having 

 myself at once succeeded in this, I have since made 

 some experiments, with the view of finding out the 

 cause of disappointment. Procuring naphtha from 

 four different places, I found that two of the samples 

 dissolved the asphaltum readily, after its being 

 brokenup, allowed to remain in the naphtha 24 hours, 

 and then heated to about 190° ; the other two had 

 no more effect upon it than is described by Mr. 

 Eowley in Science-Gossip, vol. ii., page ; 263 ; 

 clearly showing that the only difficulty is to get the 

 right quality of mineral naphtha, when it is very easy 

 to dissolve the asphaltum in it. I may say the same 

 with regaid to the india-rubber : if the sheet or any 

 other kind is used which has been previously dis- 

 solved, two or three days, occasionally shaking the 

 bottle, will generally effect a solution ; the thick lumps 

 sold for erasing pencil-marks are not suitable for 

 this purpose, being very difficult to dissolve. Before 

 making the quantity required, it is better to put a 

 spoonful of the naphtha in a small bottle, with a few 

 bits of asphaltum as a test, which will soon show its 

 dissolving power. Mineral naphtha and pure india- 

 rubber can be procured of Mr. Woolley, 69, Market 

 Street, Manchester, with which the operation may be 

 begun and finished in two days, with the application 

 of heat, or iu four clays without it. — E. Greenhough, 

 Matlock. 



Bricks oe Dashour. — A celebrated botanist and 

 palaeontologist of Vienna has recently published 

 some remarks on the bricks of the pyramids of 

 Dashour, which was built about 3,400 years before 

 our era. One of them being examined through the 

 microscope by the Professor, he discovered that the 

 mud of the Nile, out of which it was made, con- 

 tained not only a quantity of animal and vegetable 

 matter, but also fragments of many manufactured 

 substances ; whence we may conclude that Egypt 

 must have enjoyed a high degree of civilization 

 upwards of 5.000 years ago. Professor Unger has 

 been enabled by the aid of the microscope to discover 

 iu these bricks a vast number of plants which at 

 that time grew in Egypt. — Boston Post, U.S., Bee. 

 8, 1866. 



Separation of Vegetable Cells and Cu- 

 ticles. — The quickest and easiest method for 

 obtaining isolated cells is the plan devised by 

 Schultz, viz., boiling in a mixture of nitric acid and 

 chlorate of potash. After being thus treated, boil 

 in alcohol, and afterwards in distilled water. Cuticles 

 of leaves separate readily, even if they have been 

 dried for many years. Mount in glycerine, chloride 

 of calcium, or weak spirit. — Fredk. Kitton, Norwich. 



