3 4 20 SEC. 10. ELECTRICITY. 



tinfoil have been renewed recently ; but all is restored in the form in which 

 it was used by Van Marum. 



See Van Marum, " Machine Electrique," II., p. 195. 



1368. Leyden Battery of 15 jars. 



Teyler Foundation, Haarlem. 



This battery is one of 1 6 used by Van Marum for his famous experiments, 

 giving a total coated surface of 225 square feet. 



The coatings of tinfoil have been renewed recently ; the bottom of tea- 

 lead irt the case is also restored ; and the outer coating of the case bottom, 

 which Van Marum also made of tea-lead, has been replaced by zinc. 



See Van Marum "Machine Electrique," I. p. 155, and II. p. 3. 



1369. Battery of 1O one-gallon Leyden Jars. 



Frederick Guthrie. 



This battery stands in a mahogany frame. The jars stand upon perforated 

 zinc. There is an arrangement for drying them by a current of hot air. 

 The spark from this battery deflagrates a platinum wire a foot long. 



1369a. Series of Leyden Jars, with connectors, and ebonite 

 covers, 10 pieces from 90 to 100mm. high. 



Warmbrunn, Quilitz, fy Co., Berlin. 



1369b. Battery of Leyden Jars, consisting of six jars 31 2imn. 

 high, in mahogany case. Warmbrunn, Quilitz, fy Co., Berlin. 



1369c. Cylinder, on insulating support. 



Warmbrunn, Quilitz, fy Co., Berlin. 



1369d. Cylinder, with elder-pith balls. 



Warmbrunn, Quilitz, fy Co., Berlin. 



1369e. Sphere, on insulating support, with two movable hemi- 

 spheres on ebonite rods. Warmbrunn, Quilitz, $ Co., Berlin. 



1369f. Large dissected Leyden Jar. 



Warmbrunn, Quilitz, fy Co., Berlin. 



10 7O. Spiral Leyden Jar. Frederick Guthrie. 



Two sheets of ebonite, alternating with two sheets of tinfoil, are rolled up 

 together. The central knob is connected with the inner edge of one of the 

 foils ; the brass girdle is connected with the other sheet. A Leyden jar is 

 thus formed which is compact with a large surface. 



1371. Mica-plates for insulating electrical apparatus. 



Max. Raphael, Breslau. 



Mica can be rendered electrical by the least friction, hence its frequent em- 

 ployment as an excellent insulating material, especially on account of the 

 facility with which it can be worked. 



1372. Two Large Condensers, consisting of Leyden jars, 

 each 400 millimeters high and 200 millimeters in diameter. 



Borchardt, Hanover. 



