August 31, 1905] 



NA TURE 



431 



T 



THE STANDARDISATION OF SCREWS. 



^HE question of standardising screw threads and 

 limit gauges has long received the careful 

 attention of engineers, and in Great Britain con- 

 siderable advantage has accrued from the publica- 

 tion of an interim report (No. 20, April, 1905) of the 

 Engineering Standards Committee, dealing with the 

 form and pitches of screw-threads most suitable for 

 general engineering purposes. Having regard to the 

 fact that the Wh"ltworth thread is in general use 

 throughout the country, the committee does not 

 recommend any departure from this form of thread. 

 The existing Whitworth series of pitches for screws 

 from i inch to 6 inches in diameter does not, however, 

 satisfy all requirements, and the committee has 

 dravt-n up tables of standard sizes which will doubt- 

 less meet with general adoption. For all sizes of 

 screw threads below a inch in diameter the com- 

 mittee recommends the adoption of the pitches, sizes, 

 and form of thread proposed by the British Asso- 

 ciation Small Screw Gauge Committee in 1884. 



In France an influential committee of the Soci_^t^ 

 d'Encouragement pour I'lndustrie nationale, consist- 

 ing of General Sebeft and Messrs. Carpentier, 

 Sauvage, Masson, Sartiaux, and Zetter, has devoted 

 attention to the subject, and has published in the 

 current issue of the Bulletin of the society a scheme 

 for extending the international system to screws of 

 less than 6 millimetres in diameter. The committee 

 recommends the adoption, between tlie diameters of 

 I millimetre and 5-5 millimetres inclusive, of twelve 

 screws as shown in the following table : — 



Diameter Pilch 



1-25 ( 



i7S( 

 20 ( 

 2-5 ( 



Pitch 



0-25 



0-35 

 0-45 



:^} 



3'' 

 3' 

 4-0 1 



rsf 

 sol 



5-5 J 



The six largest screws of this series are those first 

 proposed by the second committee of the Chambre 

 syndicate des Industries electriques. The screws of 

 2" millimetres and of 2-5 millimetres for which the 

 pitch is 0-5 millimetre having proved too coarse, 

 have received the pitch of 0-45 millimetre. The i rnil- 

 limetre screw has received the pitch of 0.25 milli- 

 metre in order to bring the new series into accord 

 with the Thury series, which is used for very small 

 screws. The scheme appears likely to be favourably 

 received by the Swiss and German industries. 



The initial accuracy of a helical surface, as dis- 

 tinct from the sectional form of the thread, is de- 

 pendent upon the accuracy of the leading screw of 

 the machine upon which it is cut, and thus the lead- 

 ing screw becomes a generating master-gauge which 

 instead of being used solely for gauging is called 

 upon to do work involving wear. The importance 

 of maintaining the accuracy of these leading screws 

 in connection with the production of the interchange- 

 able parts of modern guns and gun mountings led 

 to the appointment in November, iqoo, of a com- 

 mittee consisting of Mr. H. F. Donaldson, chief 

 superintendent of the Royal Ordnance Factories, pre- 

 sident, Mr. R. Matthews, Lieutenant A. T. Dawson, 

 R N , Mr. H. |. Chanev, Dr. R. T. Glazebrook, 

 F.R.S., and Colonel H. C". L. Holden, R.A., F.R.S., 

 to consider the provision of standard leading screws 

 for screw-cutting lathes, and its report to the 

 secretarv of the .\rmv Council has just been pub- 

 lished. The committee finds that the only practical 

 way to obviate the difficulty found in securing abso- 

 lute interchangeability, even on short lengths of large 

 screws, is to provide centrally special machinery for 

 NO. 1870. VOL.' 72] 



the supply of large screws of certified accuracy. 

 Approval of funds for this purpose was accordingly 

 sought and obtained. The machine, which was 

 made by Messrs. Armstrong, Whitworth and Co., 

 of Manchester, was designed to secure accuracy over 

 3 feet length of screw. Measurements made after 

 the machine was installed in the special chamber 

 erected for it at the National Physical Laboratory 

 showed that the movement of the tool carriage did 

 not vary from that produced by a true screw of the 

 same reputed length by more than 0.0002 inch in its 

 full length, and after insertion of a correcting cam 

 by more than 0.000 1 inch at any one point, and that 

 corrected microscopic scale readings and independent 

 end-measure readings did not differ by more than 

 o-oooi inch at any point. The committee recommends 

 that all accurate screws required for Government 

 engineering work be supplied in future from screws 

 originated from or corrected by the standard leading- 

 screw adjusting machine at the National Physical 

 Laboratory, and that facilities be given to private 

 firms to correct heavy screws of A-inch pitch by this 

 machine. The house in which the machine is in- 

 stalled at the National Physical Laboratory presents 

 many points of interest, as the greatest possible pre- 

 cautions have been taken to maintain uniformity of 

 temperature and freedom from vibration. 



THE STERILISATION OF WATER IN THE 

 FIELD. 



IT is well known that disease is more fatal to the 

 soldier in a campaign than the bullets of the 

 enemy. Thus in the South African campaign the 

 total deaths from disease were almost exactly double 

 those due to wounds in battle. The diseases w-hich 

 persistently dog the track of an army are typhoid or 

 enteric fever, dvsentery, and, in certain countries, 

 cholera, and to these the principal mortality is due. 



As regards their incidence, much necessarily de- 

 pends on the climatic and physical conditions of the 

 country in which the war is being carried on. Both 

 in the Spanish-.'\merican war and in the South 

 African war typhoid fever proved a terrible scourge. 



These diseases are usually largely water-borne, 

 but it must be recognised are not exclusively so, 

 and, therefore, attention to the water supply alpne 

 will not wholly prevent them. In the Spanish- 

 .■Xmerican war, for instance, the commission which 

 investigated the typhoid fever epidemics of the United 

 States "Army reported that infected water was not an 

 important factor in its spread. The other agents 

 concerned in the dissemination of this disease are 

 dust and flies, blowing or carrying infection from 

 infected latrines, and gastro-intestinal disturbance, 

 the result of heat, fatigue, and bad food rendering 

 the troops more vulnerable. It cannot be doubted, 

 however, that a pure water supply would do much 

 to lessen the incidence of typhoid fever and dysentery, 

 and probablv quite prevent cholera. 



.\ pure water supply can partially be secured by 

 three methods; (i) by a careful selection of the camp- 

 ing grounds and protection of the water supply from 

 pollution ; (2) bv deep-driven artesian wells ; and (3) by 

 the sterilisation of the water; or a combination of 

 these methods mav in many instances be adopted. 

 But whatever method is applied it must be remem- 

 bered that soldiers parched with thirst will drink any 

 water that comes In their way. As regards the first 

 method, the selection of the camping grounds, &c. , 

 it is reported that it has been adopted with consider- 

 able success bv the J.-^nanese in the present campaign ; 

 a .corps of medical officers is sent on ahead to select 

 Ihc camping ground and survey the water supply; 



