clxxxviii 



NATURE 



\Oct. 2, 1879 



STANDARD AND OBSERVATORY TIMEKEEPERS. 



TRADE. 



DENT 



MARK MANUFACTURED BY E. DENT & CO. trad 



MARK 



Guineas. 

 Standard Clock, suitable for Private Residences in Town 

 or Country, or Public Institutions, beating seconds and 

 going eight days with orce winding ; in carved and 

 decorated oak or mahogany case ... ... from 35 



(o) The same, but going one month with once 

 winding ... ... ... ... ... from 



Standard Observatory Mean-time Clock 



(fl) The same, but furnished with electrical contact 

 apparatus with eccentric screw adjustments for 

 dropping a time ball, or transmitting hourly 

 signals 



Standard Observatory Sidereal Clock 



(a) The same, but furnished with electrical contact 

 apparatus with fine vertical and horizontal screw 

 adjustments for transmitting seconds, currents 

 for controlling other clocks, &c. 



(h) The same, but arranged to omit the current at 

 every 60th second, for pricking on chronograph 

 barrel, &c. 



40 

 80 



92 



80 



95 

 97 



Guineas. 



Standard Observatory Clock, of the most refmed con- 

 struction, with barometric compensation, &c. ... 160 



(a) The same, with Sir Geo. Airy's escapement ... 170 



(b) The same, with M. Leverrier's electrical contact 



system 200 



The New Standard Clock [the primary standard timekeeper oj 

 the United Kingdom) of the Royal Observatory, Greenwich, was 

 constructed by E. Dent <2^' Co., and precisely similar instruments 

 are now being made for the Royal Observatories of Spain and 

 Belgitmi. Standard Clocks of less refilled construction /or the Ob- 

 servatories of Edinburgh (Royal), Dunsink (Royal Irish), Oxford 

 (University), Ruliowa (Russian Imperial), Geneva (National 

 Swiss); and many others, Foreign and Colonial, have been 

 manufactured. 



Galvanic Chronograpbic Apparatus, for registering 



the time of occurrence of transits and other astrono- 

 mical phenomena ... ... ... ... from 120 



The Great Galvanic Chronograph of the Royal Observatoty, 

 Greenwich, and the still more powerful Apparatus for the Royal 

 Observatory, Brussels, and other smaller ones for other Obsetva- 

 lories were constructed by E. Dent &= Co. 



E. DENT & CO, 



WATCH, CLOCK, AND CHEONOMETEB MAKEBS, 

 61, STRAND, & 34, ROYAL EXCHANGE. FACTORY, GERARD STREET, LONDON. 



MICROSCOPIC SPECIALITIES. 



Series I.- 



Series V 



-24 Medical Pathological Preparations, 



in Case £,2 2 o 



,, II. — 24 Physiological Preparations, in Case 220 

 ,, III. — 24 Educational „ „ 2 2 



,, IV. — 48 Physiological ,, ,, 440 



Pathological and Physiological Preparations in great and constantly increasing variety, and of most valuable descriptions, 



30J. per doz. 



24 Preparations from the Frog, in 



Case £2. 2 o 



VI. — 24 Surgical Pathological Preparations 220 



A. — 48 Diatomacea: (selected) 



B. — 24 „ (very rare) 



2 10 o 

 I II 6 



IS J. to 



Descriptive Lists and ftdl particulars on application to 



ARTHUR C. COLE & SON, 



ST. DOMINGO HOUSE, OXFORD GARDENS, NOTTING HILL, LONDON, W 



LATE OF 62, ST. DOMINGO VALE, EVERTON, LIVERPOOL. 



CHEMICAL APPARATUS-SCIENTIFIC INSTRUMENTS. 



Apparatus for the Analysis of Water according to Professors Frankland and Bischof. 



BUNSEN'S MODIFIED FILTER PUMPS, from lOs. 81 to 67s. 



ELECTRIC LAMPS FROM 35s. UPWARDS, AND BATTERY OF 40 QUART BUNSEN'S CELLS FOR SAME AT £8. 



GEISSLER'S TUBES. 



Catalogues and Illustrations will be sent grattiitously. A Literal Discount allowed to Wholesale Buyers, 



WHOLESALE IMPORTERS and MANUFACTURERS, 



Sets of Apparatus 

 according to Professor 

 Valentin s ' ' Book of 

 Chemistry," Professor 

 Attfield's " Manual of 

 Chemistry," &c., always 

 in stock. 



AUG. BEL and CO., 



Sole Agents far Gretiet's Batteries, and Contractors to the Government. 



34, Maiden Lane, Southampton St., Strand, W.C. 



Sets of Apparatus as 

 required by the Govern- 

 ment Schools always 

 ready and kept in stock. 



CAILLETET'S APPARATUS FOR LIQUEFACTION OF OASES- 



For the convenience of Teachers and Students at the South Kensington Classes, the Science and Art Department has authorized us to keep a stock ia 

 the store-room, first floor of the building, where the different sets and other articles are always ready for delivery. 



Printed by R. Clay. Sons, and Taylor, at 7 and 8, Ere.id Street Hill. Qu-en Victoria Street, in the City of London, and published by 

 Mac.milx.an anu Co., at the Office, 29 and 30, Bedford Street, Covcnt Garden.— Thursday, October s, 1879. 



