August 31, 1906.] 



SCIENCE. 



265 



gasoline engine were presented in full. The 

 distribution of heat thus obtained is eom- 

 pai*ed with results obtained by an entropy- 

 temperature analysis of one of the indi- 

 cator diagrams in which the losses are 

 shown graphically. The paper brings out 

 the method for finding the temperature at 

 any point in the card ; the heat of the mix- 

 ture in the cylinder ; the average value for 

 the exponent of the adiabatic curves of 

 expansion and of compression and values 

 for different parts of these curves; the 

 method of obtaining the entropy for all 

 points ; and a comparison of results of some 

 recent tests at the Pennsylvania State Col- 

 lege. 



Certain conclusions are drawn from the 

 study of the subject: (1) the losses can not 

 be computed accurately unless the data are 

 taken more completely and with greater 

 care than is usual with such tests; (2) 

 about 20 per cent, of the heat of the gaso- 

 line vapor is available for useful work at 

 full load; (3) the common method of ob- 

 taining, by test, the heat in the exhaust 

 gases is not satisfactory; (4) the teaching 

 of the entropy-temperature analysis with- 

 out requiring the student to make the an- 

 alysis is a pure waste of time (the average 

 student in the senior class ought to master 

 the whole theory in a few hours, and make 

 the analysis in a few days' time, and this 

 will open to him some of the neatest appli- 

 cations of thermodynamics; a complete 

 analysis by a student is presented in the 

 paper) ; (5) the value of the exponent of 

 the true adiabatic curve is obtained from 

 the ratio of the specific heat at constant 

 pressure to the specific heat at constant 

 volume, and if this curve is constructed it 

 will bring out at a glance where heat is 

 taken in or given out, without resorting to 

 the entropy-temperature diagram. Brief 

 reference is made to the method known as 

 ' cyclic analysis, ' in which the principal re- 

 sults as mean effective pressure are ob- 



tained from the heat put in, the initial tem- 

 perature, the value of the specific heat at 

 constant volume and the temperature after 

 compression. The author has found this 

 method to contain nothing attractive as a 

 system for teaching, because, (1) it makes 

 the student a mere machine, substituting 

 in derived formulas; (2) the value of the 

 heat for each cycle can not be obtained 

 accurately by this method; and (3) it does 

 not open up clear, well-defined lines of 

 application of the principles of thermo- 

 dynamics. The paper as a whole aims to 

 make it clear what data must be obtained 

 in order to make an entropy temperature 

 analysis and how it may be made practical 

 as a method of instruction and valuable in 

 design. It further shows how the prin- 

 ciples of thermodynamics can be made as 

 clear in showing changes of heat energy as 

 of mechanical energy. In all this the 

 writer does not depreciate the value of the 

 purely analytical methods. 



The next paper was by W. W. Churchill, 

 vice-president and chief engineer of the 

 Westinghouse, Church, Kerr Company of 

 New York, on 'The Preservation of Sur- 

 face Condenser Tubes in Plants using Salt 

 or Contaminated Water Circulation, ' The 

 paper will be published in full in the Oc- 

 tober issue of Power. 



Owing to electrolytic and galvanic action 

 on the tubes of a surface condenser using 

 water containing salt or sewage for cir- 

 culation, the use of surface condensers in 

 large power plants has been very largely 

 abandoned as useless. Under ordinary cir- 

 cumstances the water bill of such a plant 

 as that described for the Long Island City 

 power house of the Pennsylvania Railroad, 

 containing when fully constructed fourteen 

 5,500 K.W, generating sets, would be in the 

 neighborhood of $100,000. An investiga- 

 tion was undertaken of possible methods 

 for preventing the rapid destruction of the 

 condenser tubes and parts of the condenser. 



