168 L. CASELLA'S CATALOGUE 



1937. ELECTRICAL TUBE, closed and rounded at both ends, with small hole at one 



end, 24 inch, long by f inch, Is. 3d. ; 36 inch, long by 1 inch '0 1 6 



Electrical Machines with Apparatus, fitted in box with lock and key. 



1938. SET OF ELECTRICAL APPARATUS, consisting of cylinder machine, 7 inch, by 



5 inch., with brass conductor, Ley den jar, hand spiral, head of hair, image 

 plate, 2 pith figures, whirl, discharger, brass chain and amalgam, in case, 



2 6 



1939. Set of Electrical Apparatus, consisting .of a best 12-inch, plate machine on 



polished mahogany stand, with double brass conductor, 1 pint Ley den jar, 

 jointed discharger with glass handle, head of hair, hand spiral, image plates, 

 pith ball stand and 6 pith balls, 2 figures, set of 3 bells, 3 yards of chain, box 

 of amalgam, and stout brass clamp in box complete . 5 10 



1940. SET OF ELECTBICAL APPARATUS, consisting of a handsome 16-inch, plate 



machine on polished mahogany stand, with improved double brass conductor, 

 battery of 6 quart Leyden jars, in tray with cover forming case, jointed discharger 

 with glass handle whirl, spiral and head of hair, image plates, 3 pith figures, pith 

 balls, set of 3 bells, orrery, Bennett's and Henley's electrometers, insulated stool, 

 exhausting syringe, falling star in vacuum tube ; thunder-house, pistol, brass 

 clamp, chain and amalgam, complete in case . . 10 10 



# * # In electrical experiments it is important that all parts of the apparatus should be 

 slightly warmed at a distance from the fire, and the old amalgam removed, the rubbers taken 

 off, warmed and scraped, and fresh amalgam applied. The machine should be firmly clamped 

 to the table, and carefully cleaned with a warm silk handkerchief. The room, also, should be 

 both warm and dry, or should it be at all damp and without fire, two or three heated irons 

 placed near the machine and renewed at intervals so as to radiate heat, and the free use of a 

 warm silk handkerchief to dust and rub all the parts, will add to its efficiency. The amalgam, 

 if too dry, may be moistened by adding a very small portion of lard. 



1941. Glass Cylinder, for showing electrical excitation, when rubbed with a warm and 



dry piece of silk or fur . . . . . 016 



1942. BRASS CYLINDER, mounted with insulating handle, for showing that metals, 



if properly insulated, become charged when excited by silk or fur 046 



1943. SOLID CYLINDERS of shellac and sealing wax, for illustrating the resinous 



electrical excitation, 5s. 6d. and . . . . 8 6 



1944. LEYDEN JARS and BATTERIES, for accumulating electricity : 



pint 026 



Pint 030 



3 pint . ,. . ,056 

 2 quart . . . .., 076 



Quart . ,-= ' . " ' ' .' V 4 



Electrical Batteries or combinations of Leyden jars varying in numbers and 



size of jars, mounted in frames, with this arrangement quantity and intensity 



of electricity may be obtained to any extent. 



1945 . ELECTRICAL BATTERY, consisting of 4 No. 2 Leyden jars in frame 140 



1946. 4 3 1 12 6 



1947. 6 3 250 

 1947*. 12 4 500 



1948. AUTOMATIC PHOTOSTAT for electric light. By this simple instrument the 



battery current is made to regulate the distance between the carbon points, 

 so that a steady and continuous light is maintained (Jig. 1948) 1 18 



