dii 



NA TURE 



[May 25, 1905 



SPECIAL ARRANGEMENTS for supplying C. H. F. MlJLLER'S world- 

 renowned FOCUS TUBES at REDUCED PRICES have been made by 

 THE MEDICAL SUPPLY ASSOCIATION, 228 Gray's Inn Road, 



^ 1 London. W.C. 



+S 



With Double Regulator fur Raising & Lowering Vacu 



Tube simllnr in si/c but of ililTerent des.gn-without Kesu' 



Large Siie (170 mm. diameter) Water Cooled £4 5 O 

 ;K*ip>t:i-ve Htfis^ post: free. 



NEW AND BEAUTIFUL PREPARATIONS IN WATSON'5 UNIQUE COLLECTION. 



Very 6ne Setiec, illustrating the development of an Asc 

 (Aspersi), 16 preparations in case 



Section through entire bud of Lily ... ... 



Beautiful Slides of Stephanoceros with cilia extended, 

 according to perfection ... ...from 3 



Lophopus crystallinus 



Vermes (Marine), various 



Section of precious Opal, with matri.\ (opaque) 



Section of Quartz with fluid cavities 



Leaf of Pampa.s Grass— very pretty section 



For ,T Guin-a a y<ar ynu can have 240 Mi 



NEW.- WATSON'S DIFFRACTION BUTTONS. A sci. 



apart are engraved. A beautifully soft ladiated appearance 



25 

 4 6 



2 6 

 1 6 



3 6 

 1 



Groups of niatomrxcea:. Spicules, &c. A large 



reduced prices ... 

 NEW Edition of Supplementary List of latest Mi< 



now ready, post free. It gives full particulars of c 

 i of Aquatic Organisms, &c., &c. 



ited on a 3 X 1 slip as : 

 ■ikirgly with low powe: 



5 6 





Trypanosoma Brucei (Tsetse fly dis 

 Malarial parasites — many phases 

 Radium for the Microscope. 

 Micro. Object. Shows scintilla 



Objective. Quite new 



cro. Slides on hire from Watson & Sons' Cabinets. Send for particulars. 

 ;ntific Novelty. These buttons are made of polished steel upon which spiral lines /.n'nr.th inch 

 is imparted by these lines, the colours being in the order of the Spectrum. Made in two sizes, 

 for 2b,'- i-inch diameter, 2/6 each ; or 6 in case for 15/- 



of Microscopes (No. 2), Microscopic Objects (No. 3), Telescopes and Field Gl.isses (No. 6), 

 Po^t free on apjdication to 



W. WATSON & SONS, (^^^^lyr"") Opticians to H.M. Government, 



313 HIGM MOLBORIM, LOF^DON^, W.C. 



Branclies-16 FORREST ROAD. EDINBURGH, and 2 EASY ROW, BIRMINGHAM. Awardeil 42 Gold and other Medals. 



or?.os»i:^£:^^r's €^js.& eii^g-ii^e:^ 



Send foi Wa 



td Catalc 



RECENTLY 

 REMODELLED. 



Represents K and L 



types, giving 3-5 H.P. 



and 5 H.P 



respectively. 



Immediate Delivery 



for Stock Sizes 



of Engines. 



GREAT REDUCTION 

 CAS CONSUMED. 



Up to the end of 1904, 



over 50,000 engines 



liave been delivered, 



representing' about 



three-quarters of a 



million actual 



horse-power. 



CR.OSSLE'V :BR,0S., X.TI>., OFEIVSHA-'W, IVTA-JJCHESTEI^. 



THE STIGMATIG LENS. 



SERIES II. FjG. 

 ^RX-riSXI DESIO]^ A^-PSX^ "WOItFS.lVIA.KrSHXF*. 



Is the best All-round Lens for either Professional or Amateur use. 



Each lens will give perfect definition <ii\\\\ full aperture to the extreme corners of the plate 

 it is sold to cover ; with smaller stops it will cover at least two sizes larger, giving perfect sharp- 

 ness all over the plate, and thus becoming a wide-angle lens of the highest excellence. Either 

 combination may be used separately, giving foci of about \\ and 2 times the length of that of 

 the lens when used intact. The advantage of thus being able to choose the best point of view, 

 irrespective of distance, will be at once apparent to the artistic worker. 



EQUIVALENT TO FOUR LENSES AT THE PRICE OF ONE. 

 Eleven Sizes are now ready, from 3J to 18 inches eq. focus. 



CATALOGUE OF HIGH-CLASS CA MERAS AND LENSES, POST FREE. 



J. H. DALLMEYER, Ltd, 25 NEWMAN ST, OTfORD ST, LONDON, W. 



M AKERS OF THE CELEBRATED DALLMEYER LENSES. 



>NS, Limited, at 7 & 8 liread Street Hill. (Jueen Victoria Street, in the City of London, and piibli'hed by Macmillan 

 in's Street, London, W.C, and The Macmillan Company, 66 Fifth Avenue, New York. — Thursday, May 25, 1905. 



