June, 1906.] 



KNOWLEDGE & SCIENTIFIC NEWS. 



46: 



Sugg-ested Improvement in Binocular Microscopes." 

 It was shown that by means of a stop with circular 

 apertures placed between the objective and the prisms 

 in an ordinary binocular, definition was greatly im- 

 proved. Wenham and Stevenson forms of binocular 

 microscopes were exhibited with and without the stops 

 suggested. A Greenough binocular with separate ob- 

 jectives and a stand fitted with the .^bbe stereoscopic 

 eyepiece were also on the table. 



Creosote as a dehydrating medium for 

 embedding irv Paraffin. 



W. Pavlow recommends the following method of de- 

 hydrating tissues prior to embedding in paraffin, instead 

 of the usual method with alcohol : The objects may be 

 fixed in any kind of fluid, and are then transferred, 

 without any other previous dehydration, to creosotum 

 fagi for 4 to 24 hours, according to their size, and 

 finally put into pure creosote for two or three hours 

 longer. On removal the superfluous creosote is taken 

 up with blotting paper, the objects are soaked in xylol 

 or toluol for an hour, and then embedded in paraffin as 

 usual. 



Carl Zeiss* New Catalogue. 



The 33rd edition of Messrs. Zeiss' new catalogue has 

 just been issued and shows certain modifications from 

 former editions, more especiidly with regard to micro- 

 scope stands, certain models having been withdrawn, 

 and others added. To their larger stands Messrs. Zeiss 

 fit their new " Berger " form of micrometer fine ad- 

 justment, \\hich is a great improvement on the older 

 form, the consequent alteration in the limb enabling 

 them to add also a convenient, yet unobtrusive, 

 handle for lifting the microscope. The provision of 

 such a handle is, however, even more necessary in the 

 older form of microscope where the whole limb, instead 

 of l>eing fixed as in the above models, is borne upon the 

 upright triangular bar of the fine adjustment, for it is 

 by this limb that the average student persists in lifting 

 his microscope. A new upright stand for rough 

 laboratory use has been added, which is fitted with a 

 coarse adjustment only, corresponding to similar stands 

 made by Leitz and other makers. Perhaps of even 

 more interest, however, to the general microscopist is 

 the fact that in the present catalogue Messrs. Zeiss 

 have considerably reduced the prices of many of their 

 achromatic objectives, the old D of ^-inch focal length, 

 for instance, being reduced from ^2 2s. to ^,"1 15s., 

 and the i-i2th inch oil immersion from ^"8 to jQ6 5s. 

 The Huygenian oculars, nose-pieces, &c., show corre- 

 sponding reductions. The apo-chromatic objectives 

 and compensating oculars, unfortunately, are not re- 

 duced in price, and amongst the former we note that 

 the one inch of .3 N..\., formerly supplied for the lo-inch 

 tube, no longer appears, .'\part from its own interest, 

 the catalogue contains much valuable information on 

 optical matters, set forth in a lucid and instructive 

 manner, but I regret to see that Messrs. Zeiss continue 

 (on page 19) to give inaccurate magnifications for the 

 compensating oculars a.s used for the Continental 

 length of tulx', and to state that when these are used 

 for the lo-inch tube " to obtain correct ocular matjni- 

 fication (the italics are my own) it is necessary to 

 multiply the figures engraved on the oculars by 1.5." 

 Of course, the ocular magnification does not vary at all 

 under such circumstances, and it is the objective magni- 

 fication that needs to be multiplied by 1.5, the total 

 magnification of (X-ular plus objective gi\ ing the same 

 result whichever method of working be adopted. The 

 practical disadvantages of the former system are that 



it leads to much confusion of thought — as only those 

 who, like myself, have frequently to answer questions 

 on the subject fully realise — that it is incorrect, and, 

 therefore, unscientific, and that it causes a worker to 

 underrate by 50 per cent, the power of the ocular which 

 lit; is using and the consequent strain which he is putting 

 upon his objective. I hope that in the next edition of 

 the catalogue this small, but not unimportant, matter 

 will receive attention. 



Microscopical Material. 



.Mr. W. S. Rogers, of .Slough, is good enough to 

 send me lor distribution some shore scrapings from 

 Adelaide, -South .'\ustraJia. The quantity is, unfor- 

 tunately, limited, but I shall be glad to send some to 

 the first applicants who send me a stamped and ad- 

 dressed envelope, and a very small box, to prevent 

 crushing of the shells. Applications must be accom- 

 panied by the coupon to be found in the advertisement 

 pages of this issue, and as I can only supply the first- 

 comers in rotation until the material is exhausted it 

 will be seen that early application is necessary. I shall, 

 however, keep a small quantity for foreign readers. I 

 am always grateful for any microscopical material for 

 distribution, and hope that any of my readers who can 

 assist me in this way will do so. 



Notes and Queries. 



Diatomaaviis Deposit. — Mr. T. W. Robertson, Glasgow, who 

 is much interested in diatoms, would be grateful if any reader 

 could assist him to get some diatomaceous deposit from the 

 province of Simbrisk, Russia, and from Seudai, Japan. Mr. 

 Robertson would be glad to defray any expense, or to know 

 of anyone Ukely to supply his wants. 



Volcanic Dust from Mont Pclce Eruption.— The Rev. W. 

 Hamilton Gordon, Farebam, Hants., would be glad if any 

 reader could give him any information as to the requisite 

 treatment for volcanic dust, and as to what points of interest 

 there are iu such dust. 



Mounting Diatoms in Realgar. — Replying to \V. H. B., Lei- 

 cester, Mr. Basil F. T. Tryon kindly sends me the following, 

 echoed from an article by Mr. J. W. Gifford in the "Illustrated 

 Annual of Microscopy" for 189S: "Realgar is prepared by 

 heating together equal parts of clear red realgar and stick 

 brimstone (flour sulphur is apt to be full of dust). In order 

 to prepare the mount a drop of the solution containing the 

 diatoms must be dried on a very thin cover-glass by passing 

 it, diatoms uppermost, through the flame of a spirit lamp. .\ 

 small piece of the medium is then placed on the glass slide, 

 which is carefully warmed in the same way by passing to and 

 fro through the flame until the medium melts, and while both 

 are still in the tlame of the lamp, the cover is turned over and 

 carefully lowered until contact is made with the medium. .As 

 soon as it has spread out to the edges a chp must be put on, 

 or the medium will crack off in cooUng, which must take place 

 very gradually. The best thing is to put the mount, still hot, 

 into a small tin bo.\, previously warmed, and place the whole 

 in a vessel of boiling water and put aside to cool. The water 

 must, of course, not touch the mount. There will be many 

 failures ; but when a good mount is made it will be well worth 

 the pains taken. This medium is very yellow, but this is no 

 objection." Mr. Tryon adds, •• I have been told that the 

 making of realgar mounts is very dangerous, on account of 

 the arsenic fumes given off iu heating. They should be pre- 

 pared in the open air and in fine weather. Damp ruins them. 

 King with Hollis' glue." 



CM.. Tunbriiigc Wells.- -I am informed that the fungi in the 

 slide you have sent nie are Triposporium elegans, one of the 

 Deniatiex. They have apparently not been yet worked out 

 and are consequently put amongst the p-ungi Imperfecti, 

 whose life history is not known. 



[Commiiniciitioiis and Eiii/uints on Mieroscopie,!! matters should be 

 addressed to F. Shillinglon Scales, •'Jersey," St. Barnabas Road, 

 Cambridge.] 



