TRANSACTIONS OF SECTION G, 677 
paper, with temperatures as ordinates and pressures as abscisse, and lines or 
curves were drawn through each set of points for which the initial pressure was 
the same. These curves, which are very nearly straight lines, are constant total 
heat curves; that is, the total heat in 1lb. of steam is the same for all points 
lying on any one curve, and the value of the total heat can be obtained from 
Regnault’s tables for the total heat of saturated steam by noting the point on the 
saturation curve where the constant total heat curve cuts it. 
Hence from this diagram, if Regnault’s tables were quite accurate, the specific 
heat of superheated steam over the range of temperature and pressure covered by 
these experiments—212° Fahr. to 890° Fahr., and from atmospheric pressure up 
to 200 lb. per square inch—could be calculated. 
Unfortunately, Regnault’s tables are not sufficiently accurate for this purpose, 
since slight errors in the values of the total heat cause large variations in the 
calculated value of the specific heat. 
The main interest, therefore, as far as the wire-drawing experiments are con- 
cerned, is in the results shown in the diagram referred to, which shows at a glance 
the whole of the experimentally obtained data. 
The paper contained diagrams illustrating the apparatus used, and also 
tables, &c., showing the conclusions that would follow if Regnault’s tables could 
be regarded as reliable enough to base such calculations upon. 
The description of the apparatus, the method of procedure, the precautions 
taken to avoid errors and to secure perfectly dry steam before expansion, cannot 
be dealt with in a short abstract. 
Experiments by a direct method have also been carried out. In these heat 
was supplied by passing a current of electricity through German-silver coils, over 
which the steam passed. The flow of steam and the electric energy supplied were 
kept as constant as possible untila steady condition was reached, and then the 
connection was obtained between rise of temperature, quantity of steam per 
minute, and watts supplied. 
Radiation was very largely avoided by causing the steam to pass through an 
arrangement of concentric passages. The loss in this way which remained was 
estimated by experiment. 
The experiments were carried out with steam at various pressures and for 
different amounts of temperature rise, but the results are not sufficiently accurate 
to enable any conclusions to be drawn as to variations of specific heat with 
‘emperature or pressure. In all cases the steam before heating was at saturation 
temperature. 
The value obtained for the specific heat at constant pressure varied between 
*36 and °45, the mean of ten experiments giving the value ‘41. 
MONDAY, AUGUST 22. 
The following Papers were read :— 
1, Electricity from Water-Power.! By A. A. CAMPBELL SwINTON. 
Though, probably, the earliest example of the production of electricity by means 
of water-power on a practical scale and its transmission to a distance was the 
installation put up at Cragside, Northumberland, by the late Lord Armstrong, in 
the year 1882, the great development of such installations has, until recently, 
taken place almost exclusively abroad. A few thousand horse-power will probably 
cover the whole of the plants of this character at present running in Great Britain; 
whereas, as was shown by a table in the paper, the aggregate horse-power of all the 
hydraulic electricity installations in the world amounts to at least one and a halt 
million horse-power, and probably reaches two million horse-power. 
By the utilisation of this water-power the author calculates that some 11,720,000 
' Published in the Hlectrical Engineer, August 26, 1904. 
