42 ELECTRIC LIGHTING. 



" i. Of a collector , which is a series of light pieces of cast iron 

 of such shapes that they present a succession of canals in which 

 circulates the heated air supplied by any source of heat. These 

 pieces present a very large surface to the motion of the hot gases, 

 which leave them at a temperature but little removed from their 

 own ; they store up the heat which they afterwards communi- 

 cate to the couples. 



" 2. Qia.diffuser of the caloric forming the outside of the appa' 

 ratus, and made of metallic plates, presenting a considerable sur- 

 face for the circulation of the surrounding air. 



" 3. Of the thermo-electric arrangement properly so called, 

 which is placed between the collector and the diffuser, so that 

 the opposite series of junctions participate in the different tem- 

 peratures of these two organs. The flow of heat takes place 

 from the collector to the diffuser through the couples, parallel to 

 their length, and without appreciable loss of .heat by the lateral 

 surfaces, thus realizing the maximum amount of transformation 

 of which the substances used are capable." 



These several plans have been realized in the apparatus 

 represented in Fig. 6, the arrangement of which also admits 

 of being varied. 



In this apparatus' the collector is formed by a cast-iron cage 

 TOP, arranged nearly like a stove for smoothing* irons, 

 underneath which is the fireplace F, wherein coke is 'burnt. 

 This cage is so formed that the current of hot air which is to 

 supply the heating effect, after having thrice circulated about 

 the apparatus by means of the chambers TOP, escapes by 

 the draught chimney A, and may, by means of stove-pipes 

 properly arranged, be used to warm a room. Externally this 

 cage forms a polyhedric surface of many faces, on which the 

 thermo-electric piles c are arranged in rows as shown ; and 

 upon these rows the diffusers D are applied. 



The diffusers are made of plates of copper arranged like 

 the leaves of a book, and are soldered on flat bands of the 

 same metal, which by means of screws are pressed firmly 

 against the rows of the thermo-electric couples. These 

 plates, by the large surface of contact they present to the air, 



