OCTOBER 27, 1899.] 
splitting racemic compounds, to the three al- 
ready known, the mechanical, the bio-chemical 
and the physical. 
dg Wy del 
LIMITATIONS OF THERMODYNAMICS. 
AN important paper has recently been issued 
from the press of Dunod as a reprint from the 
Revue de Mécanique, current volume, in which 
M, Georges Duchesne presents the results of a 
very extensive experimental study of the ther- 
mal and thermodynamic processes in operation 
in the steam engine and especially during the 
period of emission, which has been the most 
difficult of investigation and the most obscure 
of all the elements of the vapor-engine cycle.* 
With a vapor engine in steady operation the 
observation of the amount of liquid passing 
through the system in the unit of time gives 
the measure of the quantity taken into the work- 
ing cylinder at each stroke of its piston, and 
this, with the determination of ‘quality’ by 
the ‘calorimeter,’ and automatic registration of 
volumes and pressures, by the ‘indicator’ of 
Watt, permits the exact apportionment of en- 
ergies and the physical condition of the fluid 
to be determined from the instant of closure of 
the induction-valve to its opening at the com- 
mencement of exhaust. The delineation of the 
‘saturation-curve’ on the indicator-diagram, for 
the quantity of fluid known to have entered the 
-cylinder, gives the measure of contemporaneous 
volumes of the corresponding quantity of ‘dry 
and saturated’ vapor which serves as the unit of 
the scale measurements of the relative volumes, 
and weights of liquid and vapor in the mixture 
constituting the working fluid, or the extent of 
superheating, ifat any pointsuperheated. From 
the instant of commencement of emission, how- 
ever, no measure is obtainable of these quanti- 
ties, and the problem becomes incapable of so- 
lution by ordinary observation. 
Donkin has sought the solution of this par- 
ticular question of the state of the vapor in the 
period of emission and that of compression by 
the use of his ‘ revealer,’ by means of which the 
*L’état de la Vapeur a Ja Fin de l’Emission ; par 
‘Georges Duchesne, Ingénieur, ancien Assistant du 
Professeur V. Dwelshauvers-Déry ; Paris, Vve. Ch. 
_Dunod, 1899. Royal 8vo., pp. 15. 
SCIENCE. 
619 
fluid is sampled and tested as to quality, and 
Professor Carpenter, in the laboratories of Sib- 
ley College, has sought the same end by the 
use of the now familiar ‘steam-calorimeter,’ 
taking off samples of the steam automatically at 
certain points in the portion of the cycle to be 
investigated. Donkin concluded that the vapor 
in the exhaust period was wet ; Hirn, Carpen- 
ter and others, including Dwelshauvers-Dery, 
have found it dry. M. Duchesne revises the 
work of Donkin, particularly, and concludes 
that, contrary to the deduction of the investiga- 
tor himself, the research indicates that the va- 
por is dry and saturated during the period of 
emission. He decides that the results of those 
experiments furnish ‘proof of the complete 
dryness of the surface at the end of emission.’ 
If dry at this point, they will presumably con- 
tinue dry up to the beginning of the period of 
compression, and, then, mechanical compres- 
sions alone affecting the fluid, superheating 
should occur. This was the conclusion of the 
writer long before the apparatus and method of 
recent research was ready to give its testimony in 
the case,* as respects economically operated en- 
gines; but the contrary as regards uneconomical 
engines, in which the working fluid, after enter- 
ing the cylinder, is very wet, and Willans based 
upon the same conviction the details of design 
in his engine insuring that the moisture de- 
posited upon the cylinder-walls should be swept 
off as thoroughly as possible by the current of 
the working fluid. M. Duchesne finds con- 
firmation of these anticipations in the work of 
Hirn, of Delafond and of Dwelshauvers-Dery; 
the latter affording him very conclusive evi- 
dence, which he reviews at length. 
The conclusions reached are the following, in 
substance : 
(1) When, in the engine-cylinder, the vapor is 
saturated and the walls humid, the vapor and 
the water on the surface of the metal in imme- 
diate contact with the liquid assume almost 
instantaneously the same temperature. 
(2) If the surface is dry, it may take a tem- 
perature superior to that of the fluid. 
* Manual of the Steam-Engine, Vol.I., 2 53, pp. 
355-627, especially p. 631. Trans. A. 8S. M. E., 1890, - 
No. CCCLXII. ; 1894, No. DLXVI. ; 1894, 1896, pp. 
843, etc. 
