The Influence of Strain on the Properties of Matter, 503 



it possible to vary, as may be expedient, not merely the amount of 

 work done per diem, but the distribution of the work in time. In the 

 realisation of this purpose I anticipate great advantage from the use 

 of the work machine, which I have been able to construct for the 

 purpose of my inquiry by the liberality of the British Association. 



In conclusion, I would draw attention to the results relating to the 

 influence of work on the discharge of phosphates and sulphates by 

 the nrine. 



As regards phosphates, it has been shown that no increase occurs 

 unless the exertion is very severe. As regards sulphates, it mani- 

 fests itself distinctly in many cases, the output of sulphates being in 

 general terms proportional to that of nitrogenous material. 



It is a matter of regret that the total sulphur of the food was not 

 estimated. It is known that the percentage of sulphates contained 

 in the food was insignificant as compared with that excreted in the 

 urine, and consequently almost all of the discharge must have been a 

 product of oxidation. 



I beg, in conclusion, to state that the expenses of the present 

 research, which have been extremely heavy, have been defrayed by a 

 grant of the British Medical Association. I desire to express to 

 the Association my most grateful thanks. 



" The Influence of Stress and Strain on the Physical Pro- 

 perties of Matter. Part II. Electrical Conductivity {con- 

 tinued). The Alteration of the Electrical Conductivity of 

 Cobalt, Magnesium, Steel, and Platinum-iridium by Longi- 

 tudinal Traction." By Herbert Tomlinson, B.A. Commu- 

 nicated by Professor W. Grylls Adams, M.A., F.R.S. 

 Received October 7, 1884. Read November 20. 



The Alteration of the Electrical Resistance of Cobalt produced by 

 Longitudinal Traction. 



In a previous communication to the Royal Society,* I pointed out 

 that whilst with iron the electrical resistance is temporarily increased 

 by temporary longitudinal traction, that of nickel is decreased, pro- 

 vided the stress be not carried beyond a certain limit, and this, too, in 

 spite of the change of dimensions, namely, increase of length and 

 diminution of diameter, which follow from the stress. I further 

 showedf that there is a marked resemblance between the table of 

 " rotational coefficients " drawn up by Professor Hall and that laid 

 down by myself from the results of experiments on the effect of 



* " Phil. Trans.," vol. 174, p. 58. 

 f Loc. cit., p. 168. 



