1872.] Artificial Flight: An Aérial Ship. 457 
Others, again, of an opposite cast of mind, will manipulate 
their office so as to extend and develope their practice, sacri- 
ficing, if need be, every public consideration to that end. 
The vast majority, however, will simply recognise the fact, 
that to discharge the duties which are thrust upon them 
is impracticable, and will make no effort to do so. 
This aspect of the case has, naturally enough, been dis- 
cussed in medical circles. In particular, the British 
Medical Association has dire¢ted attention to it, and has 
pleaded for an allowance being made by the Chancellor of 
the Exchequer, in order to admit of adequate payment of 
the medical officers of health. 
The Public Health Act, 1872, is admittedly only the pre- 
lude to an adequate Public Health Act. Let us hope that 
its successor will, at any rate, provide for the efficiency of 
the health officers and analysts. 
V. ARTIFICIAL FLIGHT: AN AERIAL SHIP. 
and abroad, to subjugate to man the dominions of the 
air, we must give attention to the most perfect of 
aérial machines yet constructed—the aérostat of M. Dupuy 
de Lome. We have first to consider the extended study of 
the subject, in order to ascertain what had been done by 
others, and the causes of their failure, partially or in 
totality ; this, too, with the necessity of collating the data 
from which conclusions might be drawn. The conception 
may be viewed as perfected, as a means to an end, during 
the siege of Paris, when many schemes of communication 
between the besieged and those interested in their trials 
were attempted. Out of many, the machine we are about 
to describe is that only in which the difficulties presented 
by an insufficiency of principle in the science of aérostation 
have been met. It is now our obje¢t to show in what manner 
these difficulties have been overcome. 
Hydrogen gas was employed, and was obtained by the action 
of sulphuric acid and water on iron-turnings, the gas being 
afterwards washed and dried. The gas so obtained was 
calculated to exert an ascensional force of 735 to 1120 grms. 
per cubic metre, under an atmospheric pressure of 760 m.m, 
at the ordinary temperature. M. Troost, Professor at the 
Ecole Normale Supérieure, invented a varnish for the 
VOL. 11. (N-.S.) 3.N 
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ES continuing the record of what has been done, at home 
ee 
