PRESIDENT’S ADDRESS. 175 
It seems very desirable that instruments of the form proposed 
by the Home committee should be placed at the four Australian 
Observatories—at Brisbane, Port Darwin, Tasmania, and New 
Zealand, and that the observations and records should be brought 
under a uniform and controlled system. 
I must now conclude. 
It has been my endeavour to show in what direction lay the 
most urgent demands for scientific activity in these colonies con- 
cerning some of the subjects within the scope of our section. 
Whether we will be able to satisfy these demands in the 
immediate future, depends, in the majority of cases here con- 
templated, more on the attitude and support of the Australian 
Governments than on personal exertions ; for which reason the 
influence of the recommendations of this Section A, and, through 
it, that of our Association in its total capacity, may be, and, it 
is hoped, will be a determinant of success. 
No. 1.—FOUR THEOREMS IN SPHERICAL 
HARMONICS. 
By C. CoLeripcr Farr, B.Sc. 
(Read January 10, 1898.) 
No. 2.—SOME EXPRESSIONS FOR THE COMPONENT 
OF THE MAGNETIC FORCE PERPENDICULAR 
TO THE AXIS IN THE INTERIOR OF SOLENOIDS. 
By C. CoteripGe Farr, B.Sc. 
(Read January 10, 1898.) 
[ Abstract. | 
In this paper the author investigates expressions for the radial 
component of the magnetic force in the interior of a coil, and 
shows that it can be expressed in terms of the differential coefti- 
cients of the zonal harmonics. The discussion embodies six cases. 
A table of the values of the first derivatives of the first seven 
harmonics is given to facilitate numerical calculations. 
