TRANSACTIONS OF SECTION G. 879 



of electric motive power and electric traction. The attempt to supply all these 

 from one generating station has led to the use of unsuitable plant, to confusion in 

 the station itself, but at the same time to a reduction in prices charged. It has 

 also resulted in a large variation in capital cost per kilowatt of plant. Small and 

 isolated undertakings trj' to attain equally successful results by other experiments, 

 but fail. Economical production is only possible where both the generating costs 

 and the standing charges are reduced together as the load increases and the system 

 extends. To etFect this generating works must in future be constructed and 

 located witli a view to include the supply of energy for motive power, tramways, 

 and electro-chemical purposes. Details of such construction and location should 

 embody the following points : — 



(1) The machinery must be designed to generate at high voltage, differing 

 according to the extent of the area and the nature of the system, but it must be 

 suitable for transformation at sub-stations to meet all possible requirements. 



(2) The type of all boilers, engines, electric generators, switchboards, &c., must 

 be simple and mechanically reliable, even at the sacrifice of some slight maximum 

 economy. 



(3) All complicated gear and fanciful combinations, such as might lead to 

 possible breakdown, must be avoided throughout the eutire arrangement. 



(4) As far as possible the difl'erent units of the respective types of plant should 

 be uniform in design and arrangement and made to one standard size, thus econo- 

 mising in labour, avoiding large ' stand-by' plant and spare gear. 



(o) The buildings should be devoid of all unnecessary embellishments, nor 

 should an attempt be made to confine too many departments under one roof. 



(6) The location should be such as to ensure a cheap and ready supply and 

 delivery of fuel, and where condensing can be accomplished efticiently and 

 inexpensively. 



TUESDAY, SEPTEMBER 11. 

 The following Report and Papers were read : — 



1. Report on Small Screiv Gauges. See Reports, p. 436. 



2. On Screiv Threads tised in Cycle Construction, and for Scretvs subject to 

 Vibration. By O. P. Clements. 



The Chairman of the Screw Gauge Committee of this Association has honoured 

 me by the request that I would contribute a short paper on screw threads which, 

 in my experience, have proved to be the most suitable for use in cycle construction 

 and for screws that are subject to vibration. In complying with this request I 

 propose to confine myself chiedy to the consideration of what is of most importance 

 in tills connection, namely, the shape of the threads. The time limit allowed for 

 this paper would be inadequate for dealing exhaustively with such matters as 

 pitch in relation to diameters, interchangeability, and gauging. 



In my opinion it would be impossible to devise a standard thread suitable for all 

 classesof work and the various conditions of use. At piesent there are not only 

 standard threads differing so much in shape as the Whitworth and the American, 

 but also a large number of bastard threads, differing in shape from either of these, 

 and which have been adopted in most instances as a matter of expediency and 

 necessity. A too slavish use of a standard thread has no doubt often been the 

 cause of much mischief and inconvenience in its adaptation to purposes /or which 

 it was unsuitable. 



When Sir Joseph Whitworth framed his system of threads and pitches he 

 had not at his command the superior quality of steel for the mHnufacture of 

 screws which we have in the present day. If he had, I venture to think that his 

 system would have been somewhat modified both in shape of thread and in pitch. 



