184 L. CASELLA'S CATALOGUE 



2148. ABEL'S FUSEES, per dozen . . . . . . 023 



2149. CONDUCTING COPPER WIEE, with two coatings of gutta-percha, per yard, 4|d. 



2150. A Set of Five Gr OTe's Batteries, with platina plates, 5 by 2 inch., in tray 



2 18 



2152. 6i by 3 inch. 4 10 



2153. GASSIOTT'S VACUUM TUBES, in all their varieties as improved and constructed by 



L. CASELLA for Mr. Gassiott. 



2154. IMPKOVED MODEL TELEGRAPH with apparatus, book of signs and instructions, 



complete . . . . . . 450 



TIIERMO-ELECTRICAL INSTRUMENTS. 



These instruments are for demonstrating the evolution of electric currents by 

 unequally heating dissimilar metals. 



2155. COMPOUND BAR OF BISMUTH AND ANTIMONY, for exhibiting the production of 



thermo-electricity by heating its extremity, by which the needle of a delicate 

 galvanometer is deflected . . . . 8 6 



2156. COMPOUND BAR OF BISMUTH AND ANTIMONY, of larger size, on brass stand 



15 6 



2157". Melloni's Thermo-EIectric Battery (fig. 2157), p. 182, in mahogany frame, on 

 brass pedestal 2 10 



2158. MELLONI'S THERMO-ELECTRIC BATTERY, of large size, wilh movable cone, 



polished and silvered inside, on massive stand, with lengthening and jointed 

 motion, exceedingly sensitive, as used by Professor Tyndal . 4 4 



2158*. EXTRA CONE for the above . . . . . 10 6 



2159. SEEBECZ'S THERMO-ELECTRIC APPARATUS of bismuth and antimony, in which 



a magnetic needle is suspended ; an electric current is manifested by the 

 deflection of the needle on applying the flame of a spirit lamp to either 

 corner. . . . . . . . 15 



2160. Thermo-EIectric Rotation Apparatus, consisting of a horse-shoe magnet fixed 



on a stand, having a spirit lamp between its poles, upon which are mounted 

 two frames of silver and platinum ; upon lighting the lamp the frames rotate 

 in contrary directions. . . . . . 160 



2162. APPARATUS for Oersted's experiments, showing the deflection of the magnetic 



needle and its tendency to form a right angle with the wire transmitting the 

 current of electricity, with 2 cups and 3 inch, needle . 076 



2163. DITTO, DITTO, of larger size cups and 6-inch, needle . . 096 



2164. . . . 12 6 

 GALVANOMETERS, FOR MEASURING GALVANIC CURRENTS. 



2165. GALVANOSCOPE, with upright spiral coils, for close approximation to a suspended 



magnet, by which the existence of a feeble current is beautifully exhibited, 

 complete, with glass shade . . . . . 1 8 



2166. CUMMING'S GOLD LEAF GALVANOMETER . . . 180 



*#* This instrument is mounted between the poles of a powerful horse-shoe magnet, and 

 consists of a strip of gold leaf, which forms part of a galvanic current when connected with a 

 battery, the direction of the current being shown by its tendency towards either pole of 

 the magnet. 



