Liver Temperature. 287 
line. The most pressing want of the future is to devise a 
mode of investigation generally applicable in different parts 
of the world; but the choice should not be directed by any 
discussion of the physical aspects of the problem—our only 
plan, it is true, when the inquiry was first begun, but now 
out of place with an abundant experience to guide us. The 
least profitable path has been that of the speculator, whilst 
most progress has been made by the systematic plodding of 
the cautious investigator. 
I am not fitted to distinguish between one observer and 
another in these matters, but two names occur to me as I 
write, that. of M. Renou, the eminent French meteorologist, 
in connection with the Loir, and that of Dr Griffith, of the 
East India Company’s Service, in association with the 
Brahmaputra. The work of each is a model of patient 
observation, but in different fashions: Renou’s observations 
covered years, and are invaluable ; those of Griffith occupied 
only a month, and derive part of their importance from their 
locality ; in truth, the first warm corner for the controver- 
sialist will be found in the behaviour of the Brahmaputra in 
the valley of Assam. 
A more or less accurate acquaintance with the diurnal 
changes of the temperature of a river will, as I have above 
indicated, clear the ground of a good many preliminary 
difficulties. At present, however, only the material that has 
been fairly well digested will be employed, and it must be 
borne in mind that many important series of investigations 
have thus been passed over. The range of temperature 
during the cycle of the year cannot be here discussed, though 
the subject is linked closely to the one now under considera- 
tion. The material for its study is far more abundant, and 
in fact quite nine-tenths of the series of observations on river 
temperature are barren of information on the daily changes. 
It is first requisite to know whether a river preserves the 
same temperature in mid-stream and at its margin, and 
whether the temperature alters with depth. Renou informs 
us, with regard to the Loir at Venddme, that the mean 
temperature of the borders and other parts of the river 
differed only a few hundredths of a degree Centigrade. Dr 
