On Continuous-current Transformers, 157 



curiously enough there is nothing said in the description of 

 the air-thermometer by Kohlrausch as to determination of 

 the boiling-point, the "ice point" merely being determined. 

 An experimental determination of each point is, however, 

 absolutely essential. 



Addition, June 5, 1888. 



Shortly after the reading of the foregoing paper, I com- 

 menced to use the coal-gas oxygen blowpipe — employing 

 Fletcher's oxygen blowpipe and oxygen supplied in steel 

 cylinders by the Scotch and Irish Oxygen Company (Brin 

 Process). For convenience these cylinders, with the auto- 

 matic apparatus supplied by the company for reducing the 

 pressure of the gas, leave nothing to be desired ; and the use 

 of the oxygen blowpipe makes easy and simple many opera- 

 tions which were formerly all but impossible. In particular, 

 the working of Bohemian tubing becomes, without the 

 slightest exaggeration, as easy as that of common flint or 

 soft German glass ; and in addition it is a perfectly simple 

 matter to make a junction between flint glass and Bohemian 

 glass tubing (Bohemian glass does not join well with soft 

 German tubing). Another great advantage in the use of 

 oxygen with the Bohemian glass is, that the glass does not 

 become porcelainised when worked with this flame, as it does 

 when worked with the ordinary flame. 



With this new power to assist I have now abandoned com- 

 pletely the form of gauge shown in fig. 3, and instead I am 

 using a gauge in which the main part is made of flint glass 

 (stop-cocks of Bohemian glass cannot, so far as I know, be 

 procured) , but in which the air-bulb a and capillary tube c 

 arc made of Bohemian glass, and the two glasses joined 

 together a little below the bend at the top of the tube dd. I 

 have not yet been able to obtain from any of the first-class 

 makers of Bohemian tube a supply of fine capillary tubes, but 

 these I make for myself by fusing up a piece of thick wide 

 Bohemian tubing and drawing it down. 



XVIII. Note on Continuous-current Transformers. 

 By Professor Silvanus P. Thompson*. 



IT has often been proposed to distribute electric energy 

 from central stations to local distributing stations by 

 means of transformers, which receive small currents at high 

 potential and transform them into large currents at low 



' oininunicated by the Physical Society: read June 2o. 1> 



