INDUSTRIAL PROGRESS DURING THE YEAR 1876. Ixv 



Rowland has published the results of his studies on magnetic dis- 

 tribution, giving the results of experiments made in 1870-71. 



Bleekrode has investigated somewhat exhaustively the question 

 of the use of ebonite plates in electric induction machines in jDlace 

 of glass ones. He maintains that even in ordinary machines they 

 are far preferable, but that in double machines, such as the one de- 

 vised by him, they are the only kind to be used. Moreover, they 

 have important theoretical advantages in addition. 



Warren de la Rue and Muller have described the method of con- 

 struction of their new intensity battery, consisting of 3240 cells. 

 This battery is composed of plates of chloride of silver and of zinc, 

 excited by a solution of sodium or ammonium chloride a form de- 

 vised by De la Rue in 1868. The electro-motive force of this com- 

 bination is to that of the Daniell cell as 1.03 to 1 ; the mean resist- 

 ance of the entire battery is for each cell 38.5 ohms. It evolves 

 from acidulated water (1 volume sulj^huric acid and 8 of water), in 

 a voltameter having a resistance of 11 ohms, 214 cubic centimeters 

 of mixed gases per minute. The length of the spark in air, given 

 by one series of 1080 cells, w^as 0.098 millimeter ; with two such 

 series, 0.629 millimeter ; and with three, 1.623 millimeters ; being 

 directly as the square of the number of the elements used. In a 

 subsequent paper the luminous effects produced by this spark in 

 vacuum tubes are described, the striking distance being six decim- 

 eters. 



Von Waltenhofen has described a new^ form of magneto-electric 

 machine recently constructed by Siemens and Halske. It consists 

 of steel magnets for producing the field, the peculiarity of which 

 consists in their form and arrangement, which is like two V's, 



thus w, in the space between wdiich a Siemens-Alteneck armature 



revolves. The machine is easily turned by hand, and w^ith one rota- 

 tion a second gave the electro-motive force of three Bunsen cells, 

 and with three rotations one of eight. It heated to wdiiteness 30 cm. 

 of platinum wire ^ mm. thick, worked an induction coil, decomposed 

 water, etc. Tisley has also devised an improvement in the break- 

 piece of the Siemens armature, by which the effects are increased. 



Tresca has given the results of some experiments with the Gramme 

 machine, made with great care to determine the economic value 

 of this machine for the production of light. Two machines were 

 employed, one of about six times the powder of the other. The 

 number of candle-powers obtained from the first was 12,950 ; the 

 consumption of power, 7.68 horse-powers, or 1686 candles to the 

 horse-power. From the second and smaller machine the light was 

 equal to 2114 candles ; and the power consumed was equal to 2.81 

 horse-powers, being 752 candles to the horse-power, thus showing 

 the greater economy of the larger machine. The cost of the illu- 



