﻿330 Notices respecting New Books. 



vaporization is going on from the now warmer surfaces. It is just 

 possible that condensation and vaporization due to such causes as 

 adiabatic expansion and free rushes of steam do not affect the 

 amount of water deposited ou the metal surfaces : they only affect 

 the quantity of finely divided cloud. 



All engineers are now convinced that it is important to diminish 

 the amount of water present before admission ; and three methods 

 have been adopted for this which are all effective. One which waa 

 tried about thirty years ago, aud abandoned for insufficient 

 reasons, was to superheat the steam : this will probably be tried 

 again. The second was the invention of Watt : it is to heat the 

 cylinder from the outside by a steam-jacket, or a flue-jacket, or a 

 gas flame- jacket. Among all the experiments carefully carried out 

 during the last twenty years to discover whether the waste of 

 steam in the jacket was less than the saving effected by its use, we 

 think that there is not one in which the use of the jacket did not 

 lead to economy. The economy effected by the use of the jacket 

 is very much more noticeable in cylinders, which without it were 

 very wasteful. 



The third plan is that of facilitating the drainage of the cylinder. 

 "We may not be able to drain off the water-film which adherer to 

 all the inner surface of the cylinder, but we can prevent the 

 collection of water in pockets ; and there can be no doubt that it 

 is to this that the engine of the late Mi". Williams owes most of 

 its efficiency. 



We do not know that there has yet been much of an attempt to 

 hinder the condensation by the use of paint or varnish or a lubri- 

 cator ; but a very much more promising plan, which has not yet 

 been tried, and which might be of special use in non-condensing 

 engines, is that of mixing with the steam air or some vapour whose 

 condensing temperature is much less than that of steam. The 

 experiments of Prof. Osborne Eeynolds about twenty years ago 

 showed that a comparatively small amount of air very yearly 

 retarded the condensation of steam when suddenly admitted to a 

 cold vessel. Iu this connexion it will be interesting to see the 

 results of some experiments of which we have heard in which a 

 cylinder is, in alternate strokes, that of a steam-engine and that of 

 a gas-engine. 



The use of steam-engines to drive electric-lighting dynamo- 

 machines with loads which vary greatly during the twenty-four 

 hours, and especially in places where space is valuable, has given 

 prominence to the study of the behaviour of engines in which 

 nothing varies but the initial pressure of the steam. Mr. Williams 

 found that in any trial with very varying loads, when plotting 

 " water per hour W " and the indicated horse-power H. his points 

 lay in a straight line. The result is rather striking, so striking, 

 indeed, that " W a linear function of H " has already been called 

 " the Williams law." Knowing, as we do, that the missing heat 

 is proportional to the range of temperature, and using the Eankine 

 method of calculation from Hypothetical Diagrams, it is easy to 



