May 2 2, 1879] 



NATURE 



XXXI 



BARCLAY & SON, 



138, REGENT STREET, LONDON. 

 To Her Majesty and H.R.H. the Prince cf Wales. 



DUPLEX LAMPS. 

 MODERATOR LAMPS. 



READING LAMPS. 



MICROSCOPE LAMPS. 



BEST COLZA OIL. 



A I KEROSINE OIL. 



WAX, SPERM, 



AND 



PARAFFINE CANDLES. 



ILLUSTRATED ICATALOGUES POST FREE. 



W. F. STANLEY, 



Mathematical Instrument Manufacturer 



To H.M.'s Government, Council of India, Science and Art 



Department, Admiralty, &c. 



Mathematical, Drawing, and Surveying Instruments of every description, of 



the highest quality and finish, at the most moderate prices. 



Price List post free. Engine Divider to the Trade. 

 ADDRESS- 

 GREAT TURNSTILE, HOLBORN, LONDON, W.C. 



NOW READY, 

 SECOND EDITION, 



G R I F F I Ni' S 



CHEMICAL HANDICRAFT. 



PRICE ^s. ^d. POST FREE. 



A CATALOGUE OF CHEMICAL APPARATUS: 



ILLUSTRATED, CLASSIFIED, DESCRIPTIVE. 



Demy 8vo, 480 pp., Illustrated with 1,600 Woodcuts. 



Most Complete and Cheapest List of Apparatus. 



JOHN J. GRIFFIN and SONS, 22, GARRICK STREET, 

 LONDON, W.C. 



ENGRAVINGS AND ELECTROTYPES 



FOR SALE, at prices ranging from i.f. to loj., in good condition, ready for 

 printing. Small, medium size, and large engravings, comprising a great 

 variety of subjects, suitaJ>le for Publisners, Advertisers, and Amateurs. 

 Specimen of any subject required sent post free on application. 



FACSIMILK OF SIGNATURE for 3*. An exact copy of any name 

 Guaranteed. Theve signatures being engraved in bold relief, are useful for 

 Stamping Hooks, Circulars, and Documents, or Marking Linen, and made 

 type-high for ordinary Letterpress Printing. 



Sent post free to any address on receipt of 36 stamps. 



FLEET STREET, LONDON, E.C. 



ARTISTIC— To Ladies and Gentlemen with 



some leisure time, desiring to supplement their incomes, an opportunity 

 is offered of acquiring the ART of DRAWING and ENGRAVING 

 on W(J0D in a thoroughly satisfactory and perfect style. The terms 

 are moderate, and the hours can be made to suit the convenience of 

 pupils. Persons residing in the country can receive full instructioa by 

 correspondence. For further particulars call or address Mr. J. Frank- 

 UN Nash, Axtist and EngraTcr, 75, Fleet Street* Londen, E.C 



THE MINIATURE MICROSCOPE LAMP 



(REGISTERED) 

 PRICK i4«. PORTABLE TIN CASE TOR DITTO, «. U. 



JAMES HOW & Co., 



SCIENTIFIC INSTRUMENT MAKERS, 



5, ST. BRIDE ST. {late 2, Foster Lane), LONDON. 



E.D\NkRD PATERSON, 



Electrical Engineer and Scientific Apparatus Manufacturer, 



3, BEDFORD COURT, COVENT GARDEN, LONDON. 



STEAM WORKS, GRAY'S INN ROAD. 



Ezperiments in Electric Lighting carried out 



Electrual Apparatus of all descriptions for lecture Purposes 

 Loaned out. 



APPARATUS FOR CLASS DEMON- 



ST RATION and for SCIENCE SCHOOLS. 



ELECTRIC LIGHT APPARATUS. 

 SIEMEN'S and GRAMME'S DYNAMO 



MACHINES and LAMPS for Hire and Purchase. 



LARGE ASSORTMENT of RUHMKORFF 



COILS and VACUUM TUBES. 



PROFESSOR HUGHES' MICROPHONE. 

 ELECTRIC BELLS and INDICATORS. 

 TELEPHONES and TELEPHONE CALL 



BELLS, WIRE, &c., for Fixing. 



PROF. S. P. THOMPSON'S LANTERN 



SLIDE GALVANOMETER, tos. 



EDISON'S ELECTRIC PEN £8 8s. 

 ELECTRIC and MAGNETIC APPA- 

 RATUS of all Descriptions. 



New Illustrated Catalogue of (>o pages post free 6 stamps. 

 Orders over £^ carriage paid to any part of the United Kingdom. 



BUDOLPH KOENIG, 



(DR. PHIL.) 

 MANUFACTURER OF 



ACOUSTICAL INSTRUMENTS. 



TO ILLUSTRATE THE LAWS 

 AND TO PRODUCE THE PHENOMENA OF SOUND. 



PARIS, 26, HUE DE PONTOISE. 



PRICE LISTS FREE^ 



W. LADD & CO.. 



Scientific Instnunent Manufacturers 



(fl> Atttintmtni to the Rryal InlHIutiim •/ Grtat BritaiH), 



II & 12, BEAK STREET, REGENT STREET, W. 



BYRNE'S PATENT COMPOUND PLATE PNEU- 

 MATIC BATTERY for Cautery and general purposes. 



EDMUNDS' PHONOSCOPE for making Vocal Vibra- 

 tions visible in a Vacuum Tube. 



HUGHES' MICROPHONE. 



TELEPHONIC APPARATUS, Ac. 



LADD'S IMPROVED SELF CHARGING HOLT2 

 ELECTRICAL MACHINE, with 4 to 11 Plates, in- 

 do.sed in a Mahogany and Glass Case. This instmurent is 

 immediately available in any condition of the atmosphere. 

 Philosophical Apparatus of every Description. 



IBtulrated CataUgtu, SixfncK 



