262 MR. E. H. GRIFFITHS ON THE LATENT 
I would urge that the accuracy of determinations of physical constants depends on 
the amount of attention devoted to apparently trivial matters, and that in the 
absence of full information, it is impossible to rightly estimate the value of the 
results. Corrections are often rendered necessary by subsequent re-determinations 
of the constants involved, and the application of such corrections is only possible 
when the writer has given his data in full, Much valuable experimental work has 
with lapse of time become useless, owing to the author's natural reluctance to over- 
crowd his communication with details which may at the time very possibly appear 
both unnecessary and trivial. 
Although the experiments described in this paper were not commenced until 
the Summer of last year (1894), the preparation of the apparatus and the 
standardisation of the instruments has engaged my attention for a considerable 
time. Nearly the whole of the Spring and Summer of 1893 were expended in 
fruitless efforts to render the calorimeter and its connections absolutely air-tight, and 
I found it impossible to secure perfection in this respect until in the Autumn of that 
year I succeeded in obtaining an alloy, by means of which I was able to unite glass 
and metal tubes in a satisfactory manner. The calorimeter and connections had then 
to be practically reconstructed and some improvements added, which experience had 
shown to be desirable. 
My original intention was to conclude my investigations into the latent heat of 
evaporation of water over the range 10° to 60° C. before publishing my results, and, 
had it not been for two misfortunes, I think that I shouid have now completed the 
necessary experiments. An accident to the apparatus early in September involved 
a loss of about ten days, and also compelled a redetermination of the capacity for 
heat of the calorimeter. A second mischance was a temporary break-down in my 
health, which compelled me to be absent from my laboratory for some days, and on 
resuming the work I was at first able to devote but little energy to it. During the 
University Term my time is not my own, and hence, when October 13 found the 
inquiry unfinished, I was compelled to relinquish all hopes of completing my original 
scheme until the Long Vacation of 1895 should again provide me with the necessary 
leisure. 
I feel, however, that all the experimental ditticulties have been overcome, and I 
regard the work as completed at certain temperatures. I do not propose to repeat 
the observations at those temperatures, and therefore I see no necessity to defer the 
publication of the results for another twelve months. 
Again, the facts set forth in Section XI. appear to me to so strengthen the 
conclusions to which my experiments have led me as to render any postponement 
unnecessary. 
I wish to express my sincere thanks to Mr. C. T. Heycock and Mr. F. H. NEVILLE 
for many valuable suggestions, and also for their help with the experiments on 
certain critical occasions. 
