﻿328 Notices respecting New Books. 



which many modern engineering books are stuffed. On the other 

 Land, it would be easy to point out places in which a somewhat 

 fuller treatment of the subject would have been an improvement. 

 Every statement will stand examination, there being nothing 

 slipshod either in the author's knowledge of the principles of 

 science, or in his application of these principles to the exceedingly 

 complicated phenomena with which the practical engineer has to 

 deal. It is just possible that exception might be taken to the 

 author's way of speaking of the absolute zero of temperature and 

 of absolute temperature, as if we knew its scale at very low tem- 

 peratures, In this, if he is in error, he errs with 99 per cent, of 

 the writers of books. 



The book is illustrated with many woodcuts, and gives a good 

 general idea of the most recent engineering practice; but the 

 author has very rightly left out such illustrations and descriptions 

 of mere details as are far better studied in shops and in drawing- 

 offices and their usual books of reference. 



"We are glad to see a clear description of the uses of the tem- 

 perature-entropy diagrams which Mr. Macfarlane Gray has for 

 so long been endeavouring to make engineers understand. It is 

 certain that no educated engineer who practises with it for an hour 

 will ever dispense with its help in his study of a heat-engine. For 

 the study of steam-engines we have a curve whose vertical ordinate 

 is 6 the temperature and abscissa <f> the entropy of 1 lb. of water, 

 and we have another curve for 1 lb. of dry saturated steam. An 

 adiabatic line in this diagram is a vertical straight line and areas 

 represent amounts of energy as heat or work. Assuming no 

 standing water in the cylinder, or assuming that the whole mass is 

 at the same temperature, and given the feed-water per stroke as 

 well as the indicator-diagram, it is astonishing how much infor- 

 mation as to rate of reception or loss of heat and condensation or 

 vaporization is given easily by the 0, diagram. 



That the alternate heating and cooling of the cylinder is the great 

 source of waste in a steam-engine was clearly pointed out by Watt. 

 That high temperature (and therefore pressure) of the entering 

 si earn leads to greater efficiency has been more or less correctly 

 known since the time of Carnot. But these two principles are 

 antagonistic, because the second necessitates great expansion, and 

 this implies great range of temperature, and hence each of these 

 principles has been learnt and forgotten again, eulogized and con- 

 demned, several times during the last eighty years. The valuable 

 work of Rankine, which might have been of enormous use to the 

 practical men, could not be recognized by them because the actual 

 waste in well-made engines was unaccounted for by his theories ; 

 yet Clarke's experiments were made in 1855 and Isher wood's in 

 1863. Just before Eankine's death he was beginning to take the 

 missing water into account, as is evident in his memoir of John 

 Elder. Elder, in a paper read before the United Service Insti- 

 tution in 1866, showed that it was advantageous to employ a 

 compound engine with two cylinders when expanding steam to five 



