128 SCIENCE PROGRESS. 



admirable paper by Professor Rowland l which gives the 

 methods and results of all observers anterior to 1880, and 

 Miculescu 2 supplies a further list which carries us to the 

 year 1892. The results expressed in kilogrammetres range 

 from 371-6 (Hirn, 3 1857) to 488-3 (Joule, 4 1845). The 

 list contains many names well known and deservedly 

 honoured in the scientific world, but unfortunately the 

 conclusions arrived at by many of the observers are of 

 little value. 



Rowland in 1879 wrote as follows: 5 "All the results 

 so far obtained, except those of Joule, seem to be of the 

 crudest description, and even when care was apparently 

 taken in the experiment, the method seems to be de- 

 fective, or the determination is made to rest upon the 

 determination of some other constant whose value is not 

 accurately known. Again, only one or two observers have 

 compared their thermometers with the air thermometer, 

 and the error thus caused may be more than one per 

 cent. The range of temperature is also small as a general 

 rule, and the specific heat of water is assumed constant." 



With this somewhat sweeping expression of opinion I 

 am reluctantly compelled to agree, and I would add the 

 following to the list of errors committed by the observers : 

 (a) Faulty determinations of the water equivalent of the 

 calorimeter, and the assumption that its water equivalent 

 remained constant when the temperature altered ; (b) dis- 

 regard of the undoubted fact that the readings of mercury 

 thermometers vary according to their rate of rise (a cir- 

 cumstance which I may remark escaped the attention of 

 Rowland himself) ; and (c) too great similarity in the 

 conditions under which the experiments were performed, 

 corroboration being sought for by a mere repetition of the 

 experiments rather than by an alteration in the conditions, 



1 Proceedings of the American Academy, 1880. 



2 Annates de Chimie et de Physique, vol. xxvii., p. 206. 



3 Theorie Mechanique de la Chaleur, 3rd edition. 

 4 Phil. Mag., 3rd series, vol. xxiii. 

 '•'Proceedings of the American Academy, 1880. 



