FUNCTION OF CRITICISM IN ADVANCEMENT OF SCIENCE. 351 
look strange. It is also a surprise, after these subjects in a 
half a dozen books are reduced to one notation, to find how 
widespread the tendency is to go over the same ground again 
and again and yet with no real advance beyond suggestions 
as to minor details, which occur incidentally and only as 
subordinate aspects of the same truth. 
Thus we find in (1) Barometry the attempt to put Laplace’s 
equation-in a dozen different forms, which neither advance 
in any respect the real subject of the variation of the air 
pressures with the height, while in fact all these can well be 
summarized in one system, such as the International Com¬ 
mittee proposed; in (2) the Thermodynamics of the atmos¬ 
phere, the fundamental relations are capable of being stated 
in one comprehensive scheme, which shall supplant all the 
papers now referred to, and wherein there is much repetition 
of work; in (3) Terrestrial Magnetism there are a half a 
dozen schemes of coordinates and notations now afloat, 
whereas by reference to three standard canons the entire 
subject can be made to read as one; in (4) Electricity and 
Magnetism, what a diversity of formulae have been derived 
from Maxwell on the one hand and from Helmholtz on the 
other, forming now the English and the German schools; in 
(5) Astronomy and Geodesy there is the same divergence of 
processes springing from the several works of the original 
investigators, which yet might be reduced to one simple and 
comprehensive system. It seems to me that we must soon 
have a clearing-house of these fundamental matters, carried 
out radically and comprehensively. Then all authors should 
write their works in the adopted system, on the penalty of 
not being published at all. Much pretentious new knowl¬ 
edge will thus be found to be old, and all recognized advances 
will be substantial. 
We must hasten over the second canon of newness and 
oldness, to spend the rest of our limited time on the fascinat¬ 
ing topic suggested by the third case, namely, that of rank in 
the hierarchy of knowledge. This comprises the assignment 
of relative merit to those acquirements of science which as in- 
