390 
Proceedings of the Royal Society 
Hence, for 0 , we have the differential equation, 
+i 0 sin 6 + fp fsin 26 ] =0 ' (l6 ' } 
which shows that the ring oscillates rotationally according to the 
law of a horizontal magnetic needle carrying a bar of soft iron 
rigidly attached to it parallel to its magnetic axis. 
When 0 is and remains infinitely small, 6, y , and y are each 
infinitely small, x remains infinitely nearly constant, and the ring 
experiences an oscillatory motion in period 
« , Be 
V [I + (A - B)£c](I + Ax) ’• 
compounded of translation along OY and rotation round the dia- 
meter D. This result is curiously comparable with the well-known 
gyroscopic vibrations. 
3. Laboratory Notes. By Professor Tait. 
1. On Thermo-electricity. 
Messrs J. Murray and J. C. Young have been carrying out 
experimentally the idea mentioned in my former note on this 
subject. (Proc. Dec. 1870.) Their first sets of observations, of 
the results of which I subjoin a specimen, were made with an 
iron-silver and an iron-platinum, circuit working opposite ways on 
a differential galvanometer. The resistances (including the galva- 
nometer coils) were in this particular experiment 53T and 25 - 9 
B.A. units respectively, so that but very slight percentage changes 
could he produced in them by the elevation of temperature of the 
junctions. As one of a number of closely agreeing preliminary 
trials the result is extremely satisfactory, though the exact adjust- 
ment has not yet been arrived at. To show the parabolas due to 
the separate circuits, and thus exhibit the advantage of the method, 
I have requested the experimenters to break the circuits alter- 
nately after taking each reading of the complex arrangement, and 
take a rough reading. The last four columns of the table give 
the results; but, as the temperatures were probably slightly different 
from those in the first columns, no very direct comparison can be 
instituted. A glance at the 4th, 6th, and 8th columns, however, 
shows how nearly a linear relation between temperature-difference 
of junctions and galvanometer deflection has been arrived at in the 
