16G 



KNOWLEDGE. 



[Jl-LY, 1901. 



the fine adjustment is carried to its limit, and thus undue strain 

 is prevented. 



The construction presents features of originality and 

 ingenuity. Every care has been taken to obviate unequal 

 pressure, and consequent deterioration, and the whole mechanism 

 is built in an extremely solid and workmanlike fashion. 



Stringer's Fine Aciustjient (made by W. AVatson & 

 Sons). — This is, to some extent, an amplification of Watson's 

 Standard pattern. 



Fig. '). — Stnnger'fc Fine Adjustment, showing sectional view 

 of triangular fitting bar, points of contact, body tube, coarse 

 adjustment milled heads, &c. 



Fia. 6. — Sectional A'ion- of Stringer'.* Patent Fine Alljll^tment. 

 An examination of the drawings showinar the cross section of 



this fine adjustment wiU at once reveal that it is made in a 

 very substantial manner. The bar E, which is cast in one 

 piece with the limb, is triangular in shape, and fitting exactly 

 round it is a sleeve in which are grooved the dovetails that 

 receive the body of the microscope. 



The movement is effected by a lever of the second order, 

 which operates by pressure upon a steel revolving pin A. This 

 pin is mounted between two arms that are continued down- 

 wards, and are part of the sleeve fittings of the fine adjust- 

 ment, the fulcrum being at B. 



It will be seen that, contrary to the usual custom, the body is 

 drawn downwards by the lever, and upwards by the spring D. 

 A screw is provided for regulating the tension of this re- 

 actionary spring according to the angle at which the microscope 

 may be inclined. Due provision is made for adjustment for 

 wear, the frictional points of the bar E being very small, as 

 shown in the cross section drawing, and the large back jilate 

 having adjustment screws so that the fitting may be altered as 

 required. 



The rate of movement of a fine adjustment of this descrip- 

 tion would necessarily vary with the size of the limb of the 

 microscope, but the average rate of movement per turn of the 

 milled head is 'Oo m/m. 



The S]iecial virtues claimed for this fine adjustment are 

 extraordinary strength of construction, enabling it to stand 

 rough treatment, and extreme sensitiveness. There is every 

 indication that these claims are fully justified. 



NOTES AND QUERIES. 



J. /•'. A. — I have heard it stated that the blood of an habitual 

 drunkard is different in appearance microscopically to normal 

 blool. Can you tell me if this is correct, and if so, in what 

 way it differs '? 



If any reader can obtain a drop of blood from such a subject 

 and spread it on a microscope slip or cover glass, this question 

 could no doubt be settled, but I am not aware of the existence 

 of a difference. 



T. H. .V. — Of the micro.scopes you name, the D.P.H. Xo. 1 

 by Baker is unquestionably to be preferred. It is well designed 

 and soundly constructed. 



»b'. P. — Light filters are a necessity for photo-micrography of 

 coloured objects. You cannot get satisfactory contrast without 

 them. Of solutions, acetate of copper or Gifford's screen are the 

 best, but opticians sell coloured glasses which usually serve the 

 purpose. If these are used close to the lamp flame, they should 

 be optically worked, any defect in the glass being present in 

 the field of view when the condenser is focussed. If the 

 coloured glass be placed immediately beneath the condenser, 

 the optical working is not a necessity. The latter position is 

 equally as good as the former. 



Communications and enquiries nn Microscopical matters are 

 cordially inrited, and should be addressed to M. I. Oros.s, 

 Kxowi.EDfiE Office, 326, Hif/h Holhorn, W.C. 



NOTES ON COMETS AND METEORS. 



By W. F. Denning, f.r.a.s. 



C'oMKT A 1901. — A considerable number of observations of tliis 

 object have been published in the Astronomische Nachrichlen and 

 other journals. The proximity of tlie comet to the sun must liavc 

 rendered it difficiilt to detcnnine positions accui'atclj, but tliere is 

 httle doubt tliat the orbit will be satisfactorily obtained. The comet 

 was observed at various stations in Soutli Africa and Australia, it was 

 also seen at Trinidad and at ilount Hamiltim, California. But the 

 conditions of its appearance were such that it came under notice at 

 very few northern observatories. lu fact, after perilicli<m its orbit could 

 scarcely liave been more unfavourably placed with reference to observers 

 in the northern hemisjihere of the earth. The comet approached us 

 from the region west of the siai, and could only have been visible«in 

 the morning hours, then moving eastwards and curving round the 

 sun at a distance of about 15 degrees south of that luminarv, it went 

 off almost in a direct line into space just before it had got sufficientlv 

 far east of the sun to be well observed in the evening skv. But for 

 the brilliancy of the comet and the conspicuous character of its tail it 

 wouUl no doubt have entirely escaped observation. That prettv large 

 objects of this kind occasionally pass unseen is perfectly certain, for a 

 bright comet was situated close to the sun during a total eclipse on 

 May 17, 18S2, and only one view was obtained of it. The recent 



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