514 NEGJ1ETTI AND ZAMBRA, HOLBORN VIADUCT, E.G. 



3137 Fox's Circle or Inclinometer, as used on board of H.M.S. Challenger, and 



most Arctic Expeditions, for testing Terrestrial Magnetic force 38 



3138 Kew Constants Computed . 220 



3139 Thomson's Water Dropping Collector, supplied to order. 



3140 Collecting Fuse, do. do. 



3141 Portable Astatic Galvanometer, in brass case, with jewelled centres, having 



a resistance of about 1000 ohms, with controlling Magnet. In Sling 

 Leather Case 5 10 



3142 Thomson's Portable Electrometer, (attracted disc) fitted with Electrophorous 



in polished Mahogany Cabinet , 12 12 



3143 Morse Ink-recording Telegraph Instrument, or Direct Ink-writer, consisting 



of a train of wheelwork driven by a spring. Transmitting key, galvano- 

 scope, and commutator, &c., for terminal station correspondence 

 mounted on polished Mahogany ...... 21 



3144 Morse Ink-recording Instrument, with key, two galvanoscopes, commutator, 



&c., for intermediate stations, mounted as above . . . 23 



3145 Phonoscope, with Reiss' interrupter, for illustrating the principle of the 



Telephone, and showing the effect of sonorous vibrations on electrical 

 discharge in vacuum tubes 880 



3146 Long Glass Yertical Gas Jet for Singing Flame . . . . 14 



3147 Glass Tubes, 4 tuned for above, with Clip Stand . . . . 1 5 Q 



3148 Piezometer, to show the compressibility of liquids and 



liquefaction of gases under pressure with tubes . . 11 11 O 1 



3149 Cailletet's Compression Pump, for liquefaction of gases, will 



give a pressure of 300 atmospheres, without table or accessories 28 10 



3150 Ditto ditto, for 1000 atmospheres pressure . . 48 



3151 Ditto ditto, improved, producing liquefaction of 300 or 400 



grammes of Carbonic Acid per hour . . 117 



3152 Air and Water Compressing Pumps, for Testing Boilers Gauges, 



&c., &c. Supplied to Order. 



U53 APPARATUS FOR LIGHTING GAS in Public Buildings, specially con- 

 structed as required. Estimates given for fitting up Electric Bells, &c., in 

 Mansions, Hotels, Ships, &c. Also for Speaking Tubes. 



TELEGRAPHIC TESTING APPARATUS, &c. 



154 Resistance Coils Wheatstone's Bridge Relays Lightning Protectors 

 ondensors Switches, &c., &c., to order. 



