224 



Messrs. W. Macnab and E. Eistori. 



other terminal being attached to the bod}^ of the bomb outside. Thus 

 there are two electric circuits absolutely insulated from each other. 



The position of the cup which contains the explosive can be seen in 

 the figure (fig. 1), and the position of the couple in respect to the cup 



Fia. 1. 



has been varied in a way that will be explained later on. The con- 

 nections from the firing wire were led to an electric battery, which is 

 set in action when it is required to ignite the explosive. 



The connections from the thermo-couple are led to the galvanometer, 

 which is inside the recording apparatus shown in fig. 2. The general 

 details of the apparatus are well known, and have been described b)^ 

 Sir W. C. Eoberts- Austen. 



' Lime-light is used to throAv a spot of light on the mirror of the 

 galvanometer, from which it is thrown on to a photographic plate, 

 through a horizontal slit, equal in length to the breadth of the plate. 

 This photographic plate is held in a weighted frame, which falls past 

 the slit with a rate of descent uniformly regulated by clock-work, con- 



