SCIENTIFIC SUMMARY. 
197 
in practice as it has done in experiments, will introduce a fundamental 
change in the construction of the condensing engine. Hitherto the conden- 
sation of the exhaust steam has almost always been effected in the large 
separate condenser introduced by Watt, the condensation- water being pumped 
out by a large so-called air-pump. In a few instances surface condensation 
is employed, but the bulk of the condensing apparatus is then even larger 
than with Watt’s condenser. Mr. Morton and Mr. Barclay have succeeded 
in dispensing with the separate condenser and air-pump, by a beautiful 
application of the principle of Giffard’s inj ector, at the same time reducing 
the bulk of the condensing apparatus to very small dimensions. In Giffard’s 
injector there are two concentric nozzles, one communicating with a boiler 
containing steam under pressure, the other with a tank of feed- water. The 
steam rushing through the steam nozzle condenses on the jet of water and 
communicates its vis viva to the water, thus driving it forwards into 
the boiler. In the injector condenser the exhaust steam at the moment 
of condensation similarly communicates its vis viva to the water jet 
and discharges it, against the atmospheric pressure, without the need of 
employing an air-pump. A paper on this condenser was read by Professor 
Bankine before the Scottish Institution of Engineers, which will be found 
in Engineering of December 25. The chief results of Professor Eankine’s 
experiments are given in the following abstract 
Power saved by dispensing with air-pump 
Power of engines 
Mean back pressure in cylinders 
Mean vacuum in cylinders . 
Temperature of cold water 
Temperature of waste water 
1-0 Ind. H. P. 
23-8 „ 
4-0 Ibs.Jper sa. in. 
10-7 ,, 
47° E. 
8310 Y. 
Graphic determination of Stress. — Mr. J. H. Cotterill, M.A., has described 
in Engineering of January 7, the beautiful graphic methods of obtaining the 
bending moments and stresses on transversely-loaded structures, introduced 
by Professor Culman of the Zurich Polytechnic School. 
MEDICAL SCIENCE. 
Action of Alkaline Sulphates when injected into the Veins. — The experiments 
which have been recorded by MM. Jolyet and Cahours in the Archive de 
Physiologic for February are of much importance, and show how much yet 
remains to be learned concerning the physiological action of even mineral 
substances. These chemists introduced into the veins on various occasions 
sulphates of soda, potash, and magnesia, and they believe they are justified in 
drawing these conclusions : — I. That the injection into the veins of neutral 
salts (sulphates of sodium or magnesium) produces no purgation, although 
these salts are active purgatives when introduced into the intestines. 2. 
These injections, by their poisonous results, enable us to distinguish between 
the sulphates of the three salts. In reference to this latter point, the authors 
state that similar experiments have been tried before by M. Grandeau, who 
