the Thermal Unit. 435 



Him* has made some experiments on the specific heat of 

 water at low temperatures, which give the extraordinary- 

 result that its capacity for heat increases by about 6 per cent, 

 between 0° and 15°. Rowland's comment on these is as 

 follows f : — u Experiments so full of error only confuse the 

 physicist and are worse than useless." 



Jamin and Amaury made some determinations by the 

 heating of water by an electric current. Their experiments 

 were good in principle, but no precautions were taken with 

 regard to the measurement of temperature, which they re- 

 garded as a simple matter ; their results, therefore, are of no 

 value. 



Pfaundler and Platter J found variations as great as 20 per 

 cent, between 0° and 10° ! Shortly afterwards, however, 

 they published another paper which showed that the former 

 experiments were entirely erroneous. Their second series 

 showed an increase to 6° and a decrease to 13°, but their 

 temperature measurements were based entirely on a Geissler 

 thermometer. 



The experiments of M. von Munchausen § were performed in 

 an open vessel, and no reference is made to the thermometry. 



In 1879 Rowland published the results of his remarkable 

 series of experiments. The attention given by him to the 

 standardization of his thermometers and the perfection of his 

 experimental methods render his results of extreme value. 

 His experiments extended from 5° to 34° C. ; and if we accept 

 the validity of his thermometry, they establish beyond ques- 

 tion a decrease in the capacity for heat of water over nearly 

 the whole of that range, and appear to indicate a minimum 

 about 30° to 32° 0. In addition to his determinations by 

 mechanical means, he performed a series by a direct method 

 of mixtures which led to a somewhat similar conclusion, 

 except that the rate of decrease was less. 



The recent investigations of Bartoli and Stracciati || also 

 indicate a decrease in the capacity up to 20°, about which 

 temperature they find a minimum, although even over that 

 range their rate of decrease is less than Rowland's. I have 

 already published a brief criticism of their work% in which I 

 give my reasons for the conclusion that their experimental 



* Comptes JRendus, lxx. pp. 592 and 831. 

 t Proc. American Academy, vol. xv. p. 121. 

 X Pogg. Ann., 1870. 

 § Journal de Physique, 1878. 

 I| Ibid. Dec. 1893. 

 % Science Progress, April 1894. 



