NA TURE 



[September 28, 1905 



I 



All other air 

 pumps superseded. 



1 



THE. 



"GERYK" 



(Fleuss Patent) 



Vacuum Pump. 



R.esults hitherto only pos- 

 sible •with mercury pumps 

 are readily obtainable by 

 the " Geryk." Used by 

 all leading scientists. Far 

 inaore rapid than any other 



vacuum pump. 

 Price from Write for 



£4:5:0. LIST F.45. 



pulsoi 



meter engineering QSXi 



QiM eimtlreatvarhs. (Adding. 



THE NEW "STUDENT'S" 



STANDARD BAROMETER. 



(A\t. \f. A'0,-'97-) 

 This Instrumenl has been designed to meet the re- 

 quirements of Studenis and olhers who find the need of 



a Barometer which will give exact readings, and 

 cost but a moderate sum. 



appeals especially to Colleges ahd Schools fcr 



De 



The 



of the 



ell-kn 



' Fortii 



The level oft 

 1 exactly the 



cistern mercury is reducible 



imeter of the mercurial column I 



bold, well-defined reading. 1 



. of the double vernier, are capable 



inch 



lillii 



nted 



Ii hed, solid mahogany board, with plates for a 

 lent to wall, opal glass reflectors for reading of 

 :rews for vertical adjustment, 



^ etal portions are all well bronzed and lacq 



1 the scale 



edbri 



;ly recommend this Instrument for use as 



itandard " in Colleges and Schools, private Observa- 



and by Gas and other Engineers- 

 'ice, complete, mounted as illustrated, 



£3 7 6 each, 

 ay be had with one scale (either inches or milli- 

 es), and with thermometer on other scale, at same 



accurate instru* 



FULL SIZE STANDARD BAROMETER of 



same design, bore o's" diameter, inches and millimeter 

 scales, verniers reading to o'oo2 inch and oT m/m. on 

 polished mahogany board with brackets and opal glass 



reflectors, £7 1 O 



.■>,./.■ M,t>iii/ac/tinrs and Proprietors of thf Regd. Design: 



PASTORELLI & RAPKIN, Ltd., 



46 hatton garden, london, e.g. 



Wholesale Makers of all kinds of Meteorological Instruments. 



Contractors to H.M- Government. Esld. 150 years. 

 = . Telegrams : " Rapkin, London." Nat. Tel. : iqSi Holborn. 

 y difficulty be found in securing any of our instru- 

 ugh your Dealer, kindly communicate 



th 



ih us. 



INDISPENSABLE APPARATUS FOR SCIENCE LECTURERS. 



THE STROUD & RENDALL 



SCIENCE 



I) (Stroud 



LANTERN. 



.ersal Science Lantern (Fig. 

 -tent) has been devised for the projection 

 d lantern slides. In the short box in front i 

 lantern is a hinged mirror placed at an angle of 43 

 he beam ot light is reflected through a horizont 



which a slide or piece of apparatus can 



be placed. Above this is the objective 



mounted on a brass pillar, and above 



the objective a prism silvered on the 



outside. The image is rt fleeted from the 



latter to the screen, where it occupies a 



space coincident with that occupied by 



the image from the lower objective 



(which can be supplied with an erect- 

 ing prism) obtained when the mirror is 



"up" to allow horizontal projection. 



It will thus be seen that apparatus and 



slides can he made to alternate the one 



with the other by a movement of the 



- mirror. The top stage is also useful for 



Fig. I. the projectionofdrawingsand diagrams Fig. 2. 



made while the lecture is proceeding. 



The Lantern has body of mahogany lined with fireproof insulator, two doors on one side, superior compound 

 achromatic objective 6 in. focus, for horizontal projection, achromatic objective S or 10 in. locus, for vertical 

 projection, superior prism with silvered face, best quality lime-light burner, complete in case as Fig. 2 ... £7 

 Can be fitted with Arc Lif^ht or 1,000 c.p. Nernst Lamp. 



BARR & STROUD LANTERN SLIDE APPARATUS. 



{Made in accordance ivitit Pro/. Stroud's suest recent suggestions.) 



This ingenious apparatus (Fig. 3) is fitted with 

 graduated scales which enable an operator without 

 calculation or focussing on screen to quickly obtain a 

 negative of lantern size (3^ by 3^ inches). 



Price without Lens £5 10 O 



,, with Superior l{ectillr)ear Lens 7 5 



I or further Particulars sec Descriptive Circular, 



May be obtained from any Dealer, or from the only 

 authoiised makers— 



15 O 



