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SCIENCE- G OSS IP. 



President, Dr. Tatham, is printed in full and deals 

 mainly with comparatively new mounting media 

 of high refractive indices, such as a solution 

 of biniodide of mercury in potassium iodide, 

 phosphorus, quinidine, realgar, and a combina- 

 tion of piperine with bromide of antimony. All 

 these media have unfortunately their drawbacks, 

 and two at least are really dangerous in unskilled 

 hands. The Proceedings of the Club are reported 

 in full, and notice is given of the various excur- 

 sions to be held during the summer. There are 

 also several interesting papers, the most noticeable 

 of which is one on Radiolaria, by Mr. Arthur 

 Earland, which might very well serve as an intro- 

 duction to the study of these exceptionally beautiful 

 Ehizopods. This paper is illustrated by two 

 beautiful plates reproduced from the Eeport of the 

 Kadiolaria of the " Challenger " Expedition, and is 

 followed by a list of fossil Kadiolaria from Bar- 

 bados, compiled by the same author. Mr. J. G. 

 Waller writes on a hitherto undescribed British 

 sponge of the genus Mcyphiodesnia, the spicules of 

 which he illustrates ; and other members contribute 

 shorter notes on various subjects, amongst which 

 we notice one on the genus Laeinularia of the 

 Rotifera, by Mr. C. F. Rousselet. 



Preparing Wood Sections. — Sections of wood 

 for microscopical observation are of two kinds — 

 viz., those intended to display the anatomical 

 structure of the tissues only, and those intended to 

 teach something about the physiology thereof, as 

 demonstrated by chemical tests. Wood selected 

 for the former may be subjected to pretty violent 

 treatment beforehand. For instance, a piece one 

 inch diameter and about two inches long may be 

 boiled in water, then in alcohol, and extracted in 

 succession by benzene, dilute soda, and dilute 

 acid ; then a slit is cut transversely half-way 

 through it at about \ inch from one of the ends, 

 and the semi-cylindrical plate of wood of | inch 

 radius and \ inch thick removed. The smoothed 

 semicircular surface hereby formed is the place to 

 make the transverse section, which is effected, not 

 by any ordinary knife, razor, or scalpel, but by 

 a specially-constructed instrument. A suitable 

 one is a knife 3 J inches long, fths of an inch 

 broad, and over ^-th inch thick at the back ; it is 

 slightly hollowed on the lower side, very sharp, 

 and set in a solid handle, the whole being about 

 8 inches in length. It should always be carefully 

 wiped, cleaned dry after use, and kept in a well- 

 closed case. If the wood has been previously 

 treated in the manner aforesaid, no staining or 

 bleaching of the section is required ; on, the 

 contrary, they must be studiously avoided, except 

 in the case of coniferous wood, when gum styrax is 

 not the mounting medium. Sections of wood 

 required for chemical physiology are prepared 

 either from the fresh material, or from small frag- 

 ments that have been steeped or boiled beforehand 

 in various solutions. The same kind of knife is as 

 requisite here as in the former case, whilst even 

 greater care, dexterity, and " science " must be em- 

 ployed. For the detection of the more conspicuous 

 bodies, such as starch or oil, the sections may be 

 very thin ; but for the study of protoplasm and its 

 contents they must not be too thin. Such, at least, 

 seems to be the opinion of that most expert section- 

 cutter, the late Professor De Bary, whose slides, to 

 the number of some thousands, have lately been 

 acquired by one of our institutions. My own 

 opinion is that a section cut by a properly con- 



structed and fully-sharpened knife will stand, so 

 to speak, being made considerably thicker than 

 one bunglingly hacked out by a bad or indifferent 

 tool. Moreover, there is no doubt whatever that 

 the thinner the section, provided it hangs well 

 together, the better will the effect of the various 

 test reagents be visible, and the proper interpreta- 

 tion thereof be more readily attained. — (-Dr.) P. Q, 

 Keegan, Patterdale, Westmorland. 



New Cover-Glass Gauge. — It is, of course, well 

 understood that the thickness of the cover-glass 

 slightly alters the correction of an objective, though 

 this becomes serious only with high powers. This 

 necessitates readjustment either by means of a 

 correction collar or by the simpler alteration of the 

 tube-length of the microscope itself. Some day, 

 perhaps, the Royal Microscopical Society will suc- 

 ceed in standardizing the thickness of cover-glass 

 for which objectives are corrected by makers ; but 

 at present, unfortunately, there is no uniformity in 

 this respect. Messrs. R. & J. Beck : who themselves 

 correct their objectives for a cover-glass of -00b' inch, 

 have just brought out a new cover-glass gauge with 

 which to determine the thickness of the cover- 

 glass before use. We illustrate it herewith, and it 



COVER-GLASS GAUGE (1 full tUe). 



will be observed that its construction is very 

 simple. The long lever is raised and the cover- 

 glass is then inserted against the steel plate or 

 bracket and the lever lowered so that the hardened 

 steel point close to the fulcrum of the lever (shown 

 in the figure) must rest on some portion of the 

 cover-glass. The thickness can then be read off on 

 the scale in -001 inch ; thus the illustration shows 

 a cover-glass -006 inch thick. We think this gauge 

 should give measurements of quite sufficient accu- 

 racy. Its price is 21s. 



Stearine and Naphthaline Imbedding. — I 

 see you ask in Science-Gossip, vol. vi. N.S. page 

 374, for information respecting stearine and naph- 

 thaline for imbedding. Perhaps the following 

 extract from Wright's " Popular Handbook to the 

 Microscope," page 132, may be of service. I have 

 not seen the mixture mentioned elsew T here, and 

 know nothing of its value in practice. "Mr. Cole and 

 others recommend for imbedding four or five parts 

 solid paraffin and one part lard, melted together ; 

 but this often slips in the microtome tube, and it is 

 better to use a mixture of stearine and naphthaline, 

 using the less stearine the warmer the weather. 

 This is found to hold tightly." — J. Robinson, 66 

 Fairhazel Gardens, Hampstead, N.W. 



ANSWERS TO CORRESPONDENTS. 



F. B. (York). — Owing to pressure on our space, 

 the answer to your query appeared at the end of 

 the May number (Science-Gossip, vol. vi. p. 380) 

 instead of in the usual place. In the present num- 

 ber you will see also a note on preparing wood 

 sections which may be of service to you. 



