466 
POPULAR SCIENCE REVIEW. 
It will "be seen, that, so far as economy of fuel is concerned, this engine 
■attains an efficiency hardly ever reached in a heat-engine, ordinary steam- 
engines requiring 4|- bs. of coal per h.p. per hour, and the best marine 
engines 2| lbs. The common vice of air-engines, of inefficiency in the trans- 
mission of heat from the furnace to the air, Mr. Shaw obviates by passing 
the whole of the products of combustion through the cylinder ; and to this, 
doubtless, is to be attributed much of the efficiency of this engine. It re- 
mains to be seen whether the practical difficulties which beset the use of air 
at a high temperature have been overcome. The engine has been working 
for two months in the Exhibition, apparently without any irremediable 
•defect. Professor Pankin e has contributed to the pages of the Engineer a 
mathematical investigation of the action of engines of this kind. 
Solid and Laminated Armour Plates . — We have from time to time noticed 
those results of the experiments against armour-plates which can more 
strictly be considered as new scientific facts ; we may, therefore, mention 
that recent experiments have given a distinct measure of the relative resist- 
ance of solid armour as used universally in this country, and the laminated 
armour, or armour of superposed plates, generally adopted in America. In 
the earlier English experiments with cast-iron Armstrong shot, the laminated 
armour proved to be most materially weaker than solid armour, but in the 
recent experiments with chilled iron Paliiser shot with ogival formed heads, 
the difference, although still marked, is not so great. Three 7-inch targets 
were erected, one consisting of a solid plate, another of two 3^-inch plates, 
the third of three 2^-inch plates. With the 7-inch gun and Paliiser shot, a 
charge of 15 \ lbs. was required to penetrate the solid plate ; 14 lbs. to pene- 
trate the target of two plates ; and 13 lbs. to penetrate the target of three 
plates. The work done in each case is proportional to the charge. 
Strength of Iron and Steel, when subject to Vibration and repeated Changes o f 
Load. — M. Wohler has made some important experiments on this subject, 
some of the results of which, with diagrams of the apparatus employed, may 
be found in Engineering , August 23. When bars were placed so as to be 
strained alternately by tension and compression, as is the case with axles, 
the iron bars broke ultimately with 8 to 9 tons per square inch, and the steel 
bars with 12 to 15 tons. When the repeated strains were in one direction 
only, the iron required 15 to 18 tons, and the steel 22^ to 25 tons tension. 
These bars were strained transversely. Bars subjected to simple tension gave 
similar results. 
Mont Cenis Railway . — This railway, to which reference has already been 
made in these notes, is now nearly complete, the first engine and train 
having successfully made the passage from St. Michel to Susa, crossing the 
mountain barrier between France and Italy at an elevation of 6,700 feet above 
the sea. 
MEDICAL SCIENCE. 
Muscular Contraction studied under the Microscope . — The myograph which 
M. Marey employed in investigating the nature of muscular contraction is 
said by M. Eouget to give very unsatisfactory results. The opinion which 
