Manchester Memoirs, Vol. xlvii. (1903), No. 15- 3 



Influence of temperature at the drawn-out portion of the 

 tube on which the mirror is deposited. 



With the view of obtaining information as to this, I 

 used for each of the following tests 50 c.c. of a solution 

 containing -gV of a grain of arsenic trioxide per gallon. 



The tubes used are rather wider at the drawn-out parts 

 than those which I now prefer to use, the first mirrors 

 forming at a point having an internal diameter of about 

 •063 of an inch (16 mm.). 



Tube No. I, Fig. 3, shows the photographic repre- 

 sentation of the mirror obtained in the ordinary way, by 

 heating the naked tube with the top of a Bunsen flame 

 4 inches long, protected from draughts by a conical 

 chimney to within an inch of the top of the flame, as 

 previously described by me. It will be observed that two 

 deposits have formed near to each other. The first has a 

 brownish metallic appearance and the second is black. 



The result of the second experiment is shown in tube 

 No. 2 in this series. This tube was enclosed in another 

 tube between the points {a) and ib), kept at lOO'''' C. by 

 passing a current of steam through it, and half-an-inch 

 from the end of the steam jacket the tube was cooled by 

 means of a piece of tissue paper over which a current of 

 cold water was kept rapidly dropping. 



It is remarkable that the temperature of boiling water 

 prevented the formation of the mirror altogether. The 

 small ring of mirror formed just outside the beginning 

 of the steam jacket, whilst the uncondensed arsenic passed 

 for half-an-inch along the tube outside the steam jacket 

 without depositing, and only made its appearance as a 

 black deposit at the point if) where it came in contact 

 with the cooling effect of the stream of cold water. 



The outside of the tube No. 3 in the series was 



