Correspondence... 423 
The dilatation thus obtained, increased three-fold, according to M. 
Andrand, the power of the condensed air; whence he concluded that 
inorder to arrive at a practical solution of the problem, the previous 
compression could be dispensed with, and obtain at the same time the 
condensation of the air by using for this purpose part of the expansive 
force of the caloric. 
_M. Andrand has not put this idea into practice. But in the course of. 
his trials he has several times remarked an unexpected fact which we 
here mention. 
Before making his air-locomotive public, M. Andrand had had it in 
operation within his workshop. en the reservoir was well filled 
with condensed air, the fire of the dilatator was made and the iron 
— of the bottom of the cylinders were brought to a white heat. 
ne, it was only necessary to open the stop-cock of the reservoir 
'o set the machine in motion, and cause the two driving wheels to re- 
Volve. But while the apparatus was heating up, and before the valve 
Was opened, it happened several times that the machine started sponta- 
neously and communicated to the two wheels a frightful velocity. 
The phenomena continued from 30 to 40 seconds, then ceased, without 
his discovering how it was produced or why it stopped. M. Andrand 
has not succeeded in repeating itat will. Already, some three years be- 
explain everything by a word, who know the precise cause of the 
ra, steamboat explosions, the potato-disease, &c., do not fail to 
convinced that he has. been witness of the mechanical work of the 
electricity excited by the heat. . 
“Setting aside an explanation whic 
give it a continued action; t 
Moderately heated aiid fed successively with a very small quantity of air 
