10 
on which the plane is already in equilibrium. But since the axis 
passes through the middle of the two sides of the triangle, it will 
pass also necessarily through the middle of the straight line drawn 
from the vertex of the triangle to the middle of its base; hence 
the transverse lever will have its fulcrum at the middle point, and 
must consequently be equally loaded at its two ends. Hence the 
load supported by the fulcrum of the lever which forms the base 
of the triangle, and wdiich is loaded at its two ends with equal 
weights, Vvill be equal to the double weight at the vertex, and 
consequently equal to the sum of the two weights.” 
13. Wheweli in his “Mechanical Euclid” (2nd ed. p. 170) 
says that it will be found that Lagrange’s proof, if distinctly 
stated, involves some such axiom as this : — that 
“ If two forces, acting at the extremities of a straight line, and 
a single force, acting at an intermediate point of the straight line, 
produce the same effect to turn a body about another line, the twm 
forces produce at the intermediate point an effect equal to the 
single force.” 
He adds that though this axiom may be self-evident, it will 
hardly be considered as more simple than the proposition to 
be proved. Without discussing Whe well’s criticism I oh- 
serve that Lagrange ('Mec. An.’ i, 16, 19) regards forces as 
quantities which can be added and subtracted, and which 
may be regarded (ih. p. 18) as weights. He Morgan (loc. cit.) 
seems to be of opinion that the proposition that the weight 
of the whole is equal to the sum of the w^eights of all the 
parts is known only by experience. 
“Oakwal,” near Brisbane, 
Queensland, Australia, 
July 22, 1875. 
“Note on the Temperature of the Body during Ph^^sical 
Exertion,” by M. M. Pattison Muir, F.H.S.E., Assistant 
Lecturer on Chemistry, Owens College. 
In Nature, vol. xii, p. 132, appeared an account of Dr. 
Forel’s observations on body -temperature during mountain 
