CXXXVIII ‘ 8. H. BARRACLOUGH. 
that the percentage condensation increases with the initial 
pressure. Indeed, an examination of the published results of 
various series of tests goes to show that there is no evidence of 
the loss by cylinder condensation being in any way a function of 
the temperature range either from admission to exhaust, or from 
cut off to release. The temperature range of the cylinder walls, 
which has an important effect on the amount of the heat loss, is 
probably less than that of the steam, and the temperature cycle 
through which the metal near the interior surface of the cylinder — 
passes must be of a most complex character. The question of this" 
cycle and of the conditions affecting it has been ably investigated 
by Kirsch,! and has been the subject of some interesting experi 
ments by Mr. Bryan Donkin.? The plan of these experiments 
has since been considerably improved upon by the ae of 
a thermo-electric method of measuring the temperatures.” The 
various experiments however combine to make it evident, as would 
be expected from theoretical considerations, that the thickness of 
metal which passes through a regular temperature cycle is very 
small, and varies with change of working conditions, more especi 
ally with that of speed. An accurate knowledge of the temperature 
eycle of the iron would be of great assistance in determining the 
mode of variation of cylinder condensation and there seems every 
prospect of this being gained by means of the temperature “ indi- 
cator diagrams” lately obtained by Mr. E. Adams at Sibley 
College. These diagrams show the complete temperature cycle 
through which any particular part of the metal passes during one 
revolution. By taking such diagrams at different points in the 
cylinder heads and barrel and at different distances from the 
interior surface of the cylinder, an accurate knowledge of the 
temperature cycle of the metal may be expected to be obtained. 
(c) The ratio of expansion, although not itself a phy sical 
quantity, yet is directly connected with several physical quantities 
i 08 Bewegung der Wiirme in den cylinder Wandungen, Leipzig 1886. 
2 Proc. Inst. C.E., Vol. cxv. 8 Sib. Journ. Eng., June casa: 
_ 4 For an account of the =e adopted see Cassier’s Magazin @ 1894 
