SCIENCE- GOSSIP. 



interfering with vision reflects the light down 

 through the objective to the object and back again 

 to the eye. In some illuminators of this type a 

 prism covering half the field of view takes the 

 place of the disc of cover-glass. The body-tube 

 has the usual coarse and fine adjustments ; but as 

 it is inconvenient to move it when once the adjust- 

 ments have been made, the stage is provided with 



Fig. 2. Photography of Metal.s, Troostite ix a Matrix 

 op Ferrtte axd Martexsite. x 850. 



an independent rack-and-pinion focussing adjirst- 

 ment, as well as with mechanical stage and level- 

 ling screws for the object under examination. The 

 eyepieces are of the E.M.S. No. 3 gauge. The 

 workmanship and finish of this microscope are of 

 the highest class. The foot is of the solid tripod 

 form, the back leg of which might, however, with 

 advantage be extended a little more, with a view 

 to gain increased steadiness in the horizontal posi- 

 tion. The price of the stand alone is £16 16s. 



New " Diagnostic " Miceoscopb in " Mag- 

 NALIUM." — In addition to the foregoing microscope, 

 Mr. Charles Baker has also submitted for our 

 inspection a "Diagnostic" microscope (SciENCE- 

 GossiP, vol. vi., p. 182) constructed almost entirely 

 of " magnalium," an alloy of manganese and alu- 

 minium, and resembling the latter metal in appear- 

 ance. The total weight is only fourteen ounces. The 

 price of the microscope when in this alloy is £5 10s. 



Beck's Portable " London " Microscope. — 

 Messrs. Beck have recently added a portable model 

 to their list of London microscopes (see S.-G-., 

 vol. vii., p. 184), in which the back leg of the base 

 slides in, whilst the side legs fold together, the 

 stage itself being removable. In other respects 

 the instrument is the same as the ordinary model, 

 fitted with draw-tube, coarse and fine adjustments, 

 also rack-and-pinion sub-stage, but with the 

 additional advantage of packing into a leather 

 case 9^ x 4| x 2\ inches in size. The price of the 

 stand, without objectives, eye-pieces, or condenser, 

 is £6 5s. The " London " microscope is now made 

 in a cheap vertical form, without joint for inclina- 

 tion or sub-stage, and with plain brass stage with 

 wheel diaphragm, but with graduated draw-tube, 

 spiral rack-and-pinion coarse adjustment, micro- 

 meter screw fine adjustment, and double mirror, for 

 the sum of £2 13s., complete in mahogany case. 



Bausch and Lomb Microtomes.— Messrs. the 

 Bausch and Lomb Optical Company have recently 

 issued a new catalogue of microtomes, and have 



submitted to our notice several of the instruments 

 listed therein. The most important of these are 

 the Minot Automatic Rotary and Minot Automatic 

 Precision Microtomes, of elaborate construction, 

 and consequent high price, which are more espe- 

 cially designed for advanced work. The laboratory 

 microtomes of this firm are of equal excellence of 

 design and workmanship, if somewhat less elabo- 

 rate in form. In these the object to be cut is 

 raised by a screw with a feed adjustable from two 

 to sixty micra, the adjustments being so arranged 

 that any desired cutting angle or length of stroke 

 can be had. The knife itself is carried on a 

 V-shaped block. A microtome of this description, 

 with feed operated by hand-lens, is listed at 

 £10 2s., complete with knife and holder. A smaller 

 microtome is of similar design, but the object is 

 raised by a micrometer screw with a pitch of 5 mm. , 

 with a graduated head divided into a hundred parts ; 

 so that each graduation has, therefore, a value of 

 5 micra, and there is no automatic feed. This 

 microtome is specially designed for students, and 

 costs, with knife and holder, only £i lis. 8cl. A 

 very substantial table microtome, somewhat of the 

 Leitz type, costs £2 10s. Amongst new designs 

 may be mentioned a simple microtome for freezing 

 with carbon dioxide gas, which can be attached to 

 the gas cylinder. 



Mounting Web of Spider. — I found no diffi- 

 culty in mounting spiders' webs in balsam. I 

 painted a strip of varnish across the two ends of a 

 clean slide, and held this flat against the web ; the 

 slide was covered with it, and the oblong torn from 

 the web was held in position by the varnish. I 

 added two or three strands of the big stays or cords 

 supporting the web from the tree, and then left 

 the whole to dry. A few days after I poured on 

 the centre a little balsam dissolved in chloroform, 

 then dropped a cover-glass on it, and left it to 

 dry. The thinnest lines are visible, and the dirt 

 (soot) on them more so. The hawsers, as I call 

 them, show their multiple structure well. The 

 lines which compose the cross threads of the net 

 are smallest, but quite clear and simple. They 

 are as visible in balsam as flax fibre is, and there is 

 no tendency so far to dissolve. — P. W. Payne, 

 Grove Park, 8.E. 



R. & J. Beck's New ^-Inch Oil Immersion 

 Objective. — Messrs. R. & J. Beck, Limited, have 

 sent for our inspection a new i-inch oil immersion 

 objective. The extra magnifying power over a ~- 

 inch objective is of service in bacteriological and 

 malarial investigation, whilst the price is the same. 

 This lens is made with numerical apertures of l - 

 and l - 25, and sold at £4 and £5 respectively. We 

 have tested the first of these, and can speak favour- 

 ably of its performance ; the corrections are excel- 

 lent and the working distance ample, whilst the 

 aperture is sufficient for the requirements mentioned, 

 which do not need great aperture. We some- 

 times question if, in the reaction against objectives 

 of high initial magnification without corresponding 

 increases of aperture, we have not overlooked the 

 advantages that mere magnification will give us in 

 certain investigations — a magnification in excess, at 

 any rate, of the y^-inch immersion objectives that 

 are the highest powers now generally asked for, 

 and to which special attention therefore has been 

 given by opticians. The working distance certainly 

 becomes a difficulty with higher powers, but it is 

 a mistake to suppose that an objective does not 



