FOR DETACHED OBSERVATORIES. 



527 



is afterwards transmitted to a wheel, every revolution of which corre- 

 sponds to 100 litres (or determined parts of a litre) of water which has 

 pissed through the apparatus. 



We have, then, three pieces of apparatus, the motions of which are 



Fig. II. 



finally resolved into one of rotation, which, for simplicity of registration, 

 should be transformed into a rectilinear movement. The simplest means 



