176 PROCEEDINGS OF SECTION A. 
No. 3—MAGNETIC HYSTERESIS LOSSES IN FEEBLY 
MAGNETIC AND IN DIAMAGNETIC SUBSTANCES. 
By Proressor THRELFALL, M.A., AND FLORENCE Marmin. 
(Read January 10, 1898.) 
| Abstract. | 
THE paper describes an attempt made to measure the magnetic 
losses in diamagnetic substances by suspending them in a rotating 
magnetic field and measuring the deflection at any given value of 
H. ‘The apparatus is described and some of the necessary pre- 
cautions enumerated. The percentage of initial energy absorbed 
at fields varying from 200 C.G.S. to 800 C.G.8. is given for 
sulphur, selenium, and paraffin, and is shown to be about the same 
for sulphur end paraffin (00004 and -000064 respectively) and 
about ten times as great (0004) for selenium. The presence 
of iron is shown to have no special effect unless in the metallic 
state. Any want of homogeneity was found to very largely 
increase the energy loss. This suggested that the loss depends 
upon a boundary effect as well as upon the volume, though it is 
not clear how this can be. That it isso appears, however, to be the 
case from the fact that the deflection of a ferromagnetic glass bulb 
is decreased by filling the bulb with a ferromagnetic liquid, and 
increased by filling it with a diamagnetic liquid. The difficulties 
encountered in endeavouring to measure the loss in bismuth by 
this method are commented on. 
No. 4—THE TRIGONOMETRICAL SURVEY OF NEW 
SOUTH WALES, WITH MENTION OF SIMILAR 
SURVEYS IN THE OTHER AUSTRALIAN 
COLONIES. 
By 2 2 BuRBER es bees, as. 
(Read, January 10, 1898). 
INTRODUCTORY. 
In a return of the operations of the Trigonometrical Survey of 
this Colony, published a couple of years back, it is mentioned 
that in view of the accuracy attained in our primary triangulation. 
a more rigorous method of computation, than had been before 
used in our survey, had been applied in the reduction of the 
meridian series south from the Lake George Base ; also that a 
review had been made of the data afforded by the triangulation, 
