MEAStTRTNG OF AIR. 4^3 



From the weights of air sent out as given in table XII we 

 can find the temperatures which, when existing at the beginning 

 of compression stroke inside the cyHnder, woukl make the weights 

 of air taken in equal to the weights of air sent out for the differ- 

 ent tests. These figures are given in table XII (a) which shows 

 also the temperatures of atmosphere. By comparing the actual 

 increase of temperature from atmosphere to suction cham])er with 

 the hypothetical increase of temperatures from suction chamber 

 to inside cylinder it stands to reason that the discrepancies as per 

 table XII are not only due to leakage but also to the heating up 

 of the air when entering the L.I', cylinder. 



TABLE XII (a) 



Test II IV V \l 



Temperatures in Centigrade. 



Atmosphere 20.4 22.2 22.e) 21.5 



Suction Chamber 2"/."/ 31.0 31.0 30.1 



Cylinder 35.8 40.2 35.9 35.9 



Temperatures i)i Fahrenheit. 



Atmosphere 68.7 72.0 73.2 70.7 



Suction Chamber 82.0 87.8 87.0 86.2 



Cylinder ^/'>■^ >*^'44 9^^-S <K' 5 



TK.VNSACTIONS OF SOCIETIES. 



SocTH .Afkica.v Institutkix of Encixki-r.^. — Saturday, May gth : VV. 

 J. Crilcler, Pre.sident. in the chair. — '" 'I'lic primihlc of siiirlarity. and its 

 appticdion in nuicliiiic design '" : W. Alexander. The author is not aware 

 of any paper or work on machine design in which the relations hetween 

 (Hfferent-sized engines of similar type are adequately e.xplained. It was 

 therefore sought to rectify this defect, .\mongst the points of similarity 

 discussed were conditions producing the same stress intensities in corre- 

 sponding parts of machines, centrifugal whirling, speed regulators, lubrica- 

 tion, centrifugal pumps, turbines, and automobile engines, etc. 



South .-Xfkuwx Society of Civil Exctxf.krs. — Wednesday. May i.Uh: 

 F. O. Stephens, M.T.C.E.. Presideht, in the chair. — "Rail-way signalliim in 

 South Africa'': E. Dutton. The fundamental differences in working 

 between English and South African single line railways were pointed out, 

 the important requirements for signalling on single line systems, such as 

 that characterising ])ractically the whole South African mileage, were 

 stated and discussed, and tlie distinguishing features of the signalling 

 adopted as standard by the South African Railway .Administration were 

 described and illustrated. — "' TIic desfruction by Hoods of bridges on the 

 .\atal coast lines, and the erection of temporary structures" : J.Macken- 

 zie. During March, 1913, great floods caused the destruction of several 

 railway bridges on the Natal coast lines, over an area extending along 

 the whole Natal coast from the Pondoland border to a hundred miles into 

 Zululand. Details of structure of six bridges so destroyed were given, 

 togetlier with descriptions of four of the temporary bridges subsequently 

 erected. 



