190 
mining the free oxygen in an atmosphere. In the working 
of sulphuric acid chambers it has been found extremely 
valuable, and possibly may be found so for other technical 
enquiries. It is with this view that it has been offered to 
the notice of the Society. 
The following postscript to Dr. Joule’s communication 
on the Dip Circle, printed in the last number of the Pro- 
ceedings, page 171, was read: — 
“ It ought to have been mentioned in the description of 
my dip circle that the supporting balance beam should be 
bent so that the filaments of silk should form right angles 
with the arms. The equilibrium of the beam is effected by 
an adjustible weight above the knife-edge,” 
MICROSCOPICAL AND NATURAL HISTORY SECTION. 
March 29th, 1869. 
J. B. Dancer, F.R.A.S., President of the Section, in the 
Chair. 
Mr. Robert B. Smart, M.R.C.S., was elected a member of 
the Section. 
The Rev. J. E. Vize, M.A., of Calveley, communicated 
some notes respecting the kangaroos of Beeston Castle. 
These animals have been kept in an enclosure in the Castle 
grounds for about twenty years, and are now fully accli- 
matized, our severe winters never having had an injurious 
effect upon them. They find plenty of food in their enclo- 
