May, 1904.] 



KNOWLEDGl' cS: SCIENTIFIC NEWS. 



101 



BOOKS RECEIVED. 



A Sysleraatic Survey of the Organic Colouring Matters, l>v A. G. 

 Green. F.I.C., F.C.S. ^MacmilUii.) .-is. net. 



My Airships, by .\. Santos Dmnont. (Giant Richards.') 

 Illustrated : 6s. net. 



Five Years' Adventures in the Far Interior of South Africa, li\- 

 l\.("iordonl"innMiin.i;. (John Mnrray.) Illustrated; .;s. 6d.net. 



Radium and all About It, by S. Hottone. (Wliittaker cS: Co.) 

 Illustrated : is. net. 



A Text Book of tieology, by W. Jerome Harrison, I'.G.S. 

 (Blackie Cv: Son.) Illustrated :' .^s. 6d. 



Dyes, Stains, Inks, Varnishes, i'olishe-, &c., In- Thcmias Holas, 

 F.C.S.. I-M.C. iDaubarn A: Ward.) Illustrated: 6d.net. 



Metal-Working, l)v [.C. I'earson. (Murray.) Illustrated. 2s. 



Practical Slide Making, by G. T. Harris! F.K.P.S. iIlitTe.) 

 Illustrated : is. net. 



Phylogeny of Fusus and Its Allies, by .Vniadens W. Grabau. 

 (Smithsonian Institution.) 



Researches on the Attainment of Very Low Temperatures, by 

 Morris W. Travers, D.Sc. (Smithsonian Institution.) 



Nature's Story of the Year, by C. .V. W'itchell. ( Mslier Lnwin.) 

 Illustrated : 5s. 



Notes on the Composition of Scientific Papers, by T. C. .\llbult, 

 M.A., M.D., ,.S;c. (M.icmillan.i js. net. 



TKe AitcKison Prism Field Glasses. 



The .■\itehison Prism Field Glasses, specimens of which have 

 been sent to us for review, represent a considerable .adaptability 

 alike of mind and of method on the part of British opticians. 

 The eftectiveness and popularity of the Continental prism 

 sjlasses were such as to leave no doubt in the mind of 

 opticians that in imitation lav the only form of successful 

 competition, and that to imitation must be added improve- 

 ment. In consequence a t;reat deal of money has been spent 

 with this end in view; and the .\itchison glasses represent a 

 very gratifying measure of achievement as a return on the 

 outlay of expense and ingenuity. The principal features of the 

 glasses that we have before us are the use of large object 

 glasses, variable diaphragms, and improved means of 

 focussing. With the larger object glasses are used prisms and 



I«PR1SM-/XI? 



The Black Line with arrow head shows the path of rays of light in 

 the New Aitchison Prism Field Qlass. 



lenses of a higher index of rtfr.iction than ordinarily employed. 

 The prisms are very much larger than in the German glasses. 

 The introduction of variable diaphragms is a quite nt'w 

 departure in the construction of field glasses. A p.air of Iris 

 diaphragms are in this case introduced into the tubes close to 

 the object glasses and ground together so that they are 

 worked simultaneously from the toothed wheel on the central 

 pillar. By this means, as in tlie photograpliic camera, .all 

 unnecessary rays can be cut off when the light is brilliant, 

 and in dull weather and at night the whole available aperture 

 of the object glasses can be used, thereby effecting an immense 



ad\ .intage over the old form with fixed diaphragms. Another 

 benefit is the rigidity of the body, which is secured by 

 casting the two lubes and crossbars in one piece inste.id of 

 building them up in separate parts as hitherto 



University College Lectures. 



Th- /ollou'iiig Courses 0/ Lectuycs wilL he dclivo'c.i duri)h^ May 



at the University CoUcj^e, Loiu/oii. 

 Coursoof K) Lectures on the HISTORY OF M()Dl';im 



I'lIILOSOl'llV, by Mr. .\. Wolf, M...\. First 



Lecture, .\pril 26th, 4 p.m. 

 Course of Lectures on COM PAR ATI Vb: LAW, by 



I'rof. Sir John Macdonei.i,, ^L.\., LL.L)., (".]]. 



Commencing April 26th. 

 Courseof 10 Lectures on the HISTORY OF ARCHL 



TLCTUKAL DICXliLOPMlCNT, by I'lol. F. M. 



SniHsoN. Commencing April 2jnd, 11 a.m. 

 Introductory Course of 12 Lectures on IDICALISTIC 



ETHICS, i)y Rrof. G. n.wvts Hu ks, M.A., Ph.D. 



Tuesdays and Thursdays, 5 p.m. Commencing 



April 26tli. 

 Course of liight Lectures on POST-ARISToTELl AN 



PHILOSOPHY, by Prof. G. JXwves Hicks, M.A., 



Ph.U. Tuesdays, 4 p.m. Commencing May 3rd. 



,/*^ •'^ ^^ "^^ -^^ 



Recent Patents. 



FIG. 3 



d' 



Oy 



b 



I9,6s2. Electricity, measuring. Naluek, F. II., and 

 -Xaldek linos, AND Tumnsox, i-\, yueen Street, London. 

 Sept. s. 



Currtnl Meiers. — An am- 

 meter or volt-meter, having 

 a soft-iron needle movable 

 about an axis at right- 

 angles to the magnetic axis 

 of a coil .;, is provided with 

 a magnetic shield h, //* of 

 soft iron or mild steel, 

 which may be enclosed in 

 an ordinary cast-iron cas- 

 ing. The shield has the 



form of a cubical box surrounding the coil, its ends being open. It 



may be in two parts, as shown, one overlapping the other tightly. 



Or it may be in one piece, the ends of which are overlapped. 



23. 73'- Variable=speed mechanism. Mhisckkk Smith, W, 

 and Mkisciikk-S.mhii, (i V . lioth nf 7, Kiie DruucM, I'aris. 

 Oct. JO 



KL-latoi to variable-speed mechanism, 

 particularly for use with motorcars and in 

 connection with friction-ratclietdriving-ap- 

 paratus, such as isdescribed in Specification 

 No. 20,135, A.D, igo2. A crank « mounted 

 on a shaft c has the crank-pin /( mounted on 

 anut/, wliich can move on ascrew/Mn the 

 crank ii for producing a variable throw. The 

 screw /( terminates in a worm-wheel I, 

 which gears with the worm c on a sliort 

 shaft carrying a pinion d. The piniun d 

 engages with both a loose toothed wlieel/, 

 and a loose inner toothed ring g. The 

 wheel / is fixed to the disc w so that either 

 /org can be retarded by a brake. When 

 either is retarded, the piiiicjii d is caused 

 to rotate, and, througli it, the screw A and 

 the nut i relatively to the crank u. 



