JAMES SWIFT & SON L TD, Makers of the Highest Grade

MICROSCOPES AND ACCESSORIES (M~tr. , '~ ' . . ."M i r l f N,'ie. ti,lic l;elu(~t,~e,~t~ or H.3I. (iu~er. tr~e,~t.

Petrological Microscopes " P r i m e x , " " A d v a n c e d S t u d e n L " " P e ~ r o s , " " S u r v e y " a n d " D i c ~ " ~ o d e l s i b r a l l c l a s s e s o f ~ e t r o l o g i e a l a n d N [ i n e r a i o g i c a l R e s e a r c h .

Petrological Accessories a n d I n s t r u m e n t ~ o r M [ i n e r a l o g y a n d C r y s t a l - l o g r a p h y , i n c l u d i n g R o f r a e t o m e ~ e r s , G o n i o -

m e t e r ~ , R e c o r d l a ~ I ~ J c r o m c t e r - , e t c .

[ll~strated Descriptive C,~talo.ques o,~ req~,est. ' " 4 d ~ a n c e ] S t u , ] e , ~ t '

Univers i ty Opt ical W o r k s 81 T O T T E N H A M COURT ROAD~ LONDON.

& U N I Q U E C A M E R A

LEiCA FOCAL PLANE FILM CAMERA 36 exposu re s w i t h o u t re loading . L e i t z A n a s t i g m a t i c F 3.5 lens.

Size of n e g a t i v e s 36 • 24 mm. M a d e by Le i t z w i t h t he same p r e c i s i o n - a s t h e i r m ic roscopes .

Unequalled for strength, compactness, reliability, and rapidity in use. The turningof a milled head advances film and sets shutter s~multaneously. Impossible to make blank

�9 ~r double exposuJes. New type direct vieu-flnder. The simplest of all cameras to use. Ideal for travellers a r d touri.ts.

" Superlative piece of me(hani ,m; a s~ngnlarlv efficient, practical instrument, capable o covering a wide category of work."--Vide " lhe Photogq.a2c, hic Jonrnal," March, 1926.

Price of Camera, with three spools taking fl~ms for le~8 exi~osures , complete, in leather case . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . s ~ 0 The name wi~h Distan~.e Meter . . . . . . . . . . : . . . . . . . . . . . . . . . . s 0 0

Ask f o r the. Leiea Booklet, post free.

0GILVY & C0., 20 ~Icrtimer Street, LONDON, W. 1 A l s o A g e n t s f o r t h e H e i d o s c o p e S t e r e o - l ~ e f l e x C a m e r a s a n d

L e i t z P r i s m B i n o c u l a r s .

JAMES SWIFT SON U p, M a k e r s o f t h e H i g h e s t G r a d e

HICROSCOPES AND ACCESSORIES Contr_ac'tors to alt Scientific Depar~rne~ts of H.M. GovernmenL

'" Advance~ Student'

Petrological gicroscopes " P ~ i m e x , " " A d v a n c e d S tuden t , " " P e t r o s , " " S u r v e y " and " D i c k " .w odels for all classes of Petrological and Mineralogical Research .

PetrologicalAccessories and I n s t r u m e n t s for Minera logy and Crystal- lography, including Ref rac tomete r s , Gonio-

meters , Reco rd ing M.crometers , etc. _

[llastrate~ Deseriptioe C~talojues o~ req~rest.

University Optical Works 81 TOTTENHAM COURT ROAD, LONDON.

W H A T T H E E X P E R T S S A Y "The Leioa Automatic Film Camera is a superlative piece of mechanism. I t is in all respects a singularly efficient, practical instrument, capable of cover'ng a wide category of work. The firder gives an exceedingly bri]liant, sharp image of the field in all conditions of lighting."--The Photographic Journat (the official organ of the Royal Photographic Society), March, ~ 92~.

" A camera which is unique and efficient, both terms being scientifically accurate. The camera is a marvel of diminutiveness and portability, and eminently suir for travel]ers and tourists ."--The Camera, May, ]9z5.

" A camera of decidedly novel design and a high-class instrument of precision. The definition at full aperture is excellent, and the view- finder places the subject correctly in all cases."

The Amateur Photographer, May z-, 19,. 5.

" An innovation in pocket cameras, with an excellent direct-vlsion finder. The design and workmanship are of the highest description."

The British Journa~ of PhotograThy, June, I925.

Ask for the Leica Booklet, post free

OGILVY & CO., 20 Mortimer Street, LONDON, W. 1

" ' " ' " SWIFT & SON LTD, ters of the Highest 6rade

;COPES & ACCESSORIES s to all Scientific Departments of

H.~ll. Gover~ment.

" U N I V E R S A L T E C H N I C A L " M I C R O S C O P E Perfectly adapted for the most ex- acting investigations in PETROLOGY, M I N E R A L O G t Y ~ C R Y S T A L L O G R A P H Y ,

etc., while the addition nf a special vertical illuminator with self- contained electric lamp allows of its being used for the examination of Metals and other Opaque Bodies.

_ _ _ _

Descriptive circular se~t ou request

UHIVERSlTY OPTICAL WORKS"

81 TOTTENHAM cOURT RD., LONDON W.1

PETROLOGICAL MICROE SIMPLE CLASS MICROSCOPES IM:

STAND I I I ~ (as illustrated), with fine adjustment.

LARGE PETROLOGICAL WORKINC SCOPES, with rotating com- pound mechanical stage and large illuminating apparatus.

LARGE PETROLOGICAL STAND with Synchronous Nieols.

FEDOROW'S UNIVERSAL RE- VOLVING STAGE and aux- iliary apparatus.

~ particulars in ~ist 101 sent, on request, by the British ReFrese~- tatives :

C A R L Z E I S S ( L O N D O N ) L T D . W i n s l e y H o u s e , We l l s S t ree t , Oxfo rd S t ree t , L o n d o n , W . 1 .

SWIFT & SON LTD. kers of the Highest Grade

EOPE8 & AOOE880RIES s to all Scie~tific .Departments of

H.M. Gover~J~qte~lt.

" U N I V E R S A L T E C H N I C A L " M I C R O S C O P E Perfectly adapted for the most ex. acting investigations in PETROLOGY, MI~ERALOOY, CRYBTALLOGRAPH Y~ etc., while the addition ~f a special vertical illuminator wflh self- contained electric lamp allows of it~ bein,~ u~ed for the examination of Metals and other Opaque Bodies.

Desoripti~,e circular seM o~ request

UNIVERSITY OPTICAL WORKS :

81 TOTTENHAM COURT RD., LONDON W.I

E I S CRYSTAL GONIOMETER AND SPECTROMETER

Adapted for the observation of sm~ll and defective crystal faces.

This instrument takes the form of a DOUBLE CIRCLE CRYSTXL GONIOMETER, readily convertible into a SINGLE CIRCLE GONIO-

METER and SPECTROMETER.

See detailed description by C. Pulfrich in Winkelmanns' Hand- buch der Physik, 2nd edition, volume vi., 1906, p. 58~.

THE ABBE-PIJLFRICH CRYSTAL REFRACTOMETER utilises the total reflection method, and enables the p r i nc ipa l refractive indices and principal planes of the crystal to be deter-

mined from observation of a single p~lish~d surface.

F~d~ particulars of Zeiss Opticat Equipment for Mi~eralogica~ Observations in Booktet 101/449 sent, on request, by the

.British Represe~datires :

CARL ZEISS (LONDON) LTD. Winsl~y House, Wells Street, Oxford Street, London, W.l .