Address of Sir Wm. Thomson at the Glasgow Meeting. 251 
points of the period. If x and y represent the co-ordinates of 
the axis of instantaneous rotation on June 80, 1864, then the 
observations of the separate months gave the following values of 
aand y:— 
a Weight. y Weight. 
January -- — 0°35 nee 10 ke + 0°32 
February -- — 0°03 es 14 pak + 0:09 
March oe O17 as 16. + 0-16 
ae Sao T Saas go ae ree 
May .. -- + 0°08 Tae 16 ies + 0°02 
yume .. .. — OO1 ce 14 ae — 0°01 
July — 0°05 ee 14 ist: — 0:00 
ugust -- — 0°24 meg 14 oe + 0°29 
September _. + 0°18 1B. 14 a + 0°21 
October .. + 0°13 Pe 14 tas — 0°01 
November + 0°08 pay 17 are 0°30 
December — 0°08 eis iii se — 008 
Mean 0-01-03 + 0’ -05+'"'03 : 
Accepting these results as real they would indicate a radius 
of rotation of the instantaneous axis amounting, at the earth's 
; ess of the co-efficient over its probable 
error is so slight that this result cannot be accepted as any- 
thing more than a consequence of the unavoidable errors of 
”) 
From the discordant character of these results we must not, 
however, infer that the deviations indicated by Peters, Maxwell, 
and Newcomb are unreal. On the contrary, any that fall within 
axis 
As for geological upheavals and subsidences, if on a very large 
ce ot area, they sit produce, on the eriod and axis of the 
earth’s rotation, effects comparable with those p uced by 
changes of sea-level equal to them in vertical amount. For 
simplicity, calculating as if the earth were of equal density 
throughout, I find that an upheaval of all the earth’s surface 1n 
say, of the axis of maximum inertia from the instantaneous 
