400 TRANSACTIONS OF SECTION A. 
It is suggested that in future study the velocity of the storm centre should 
be taken as unity and the component air currents classified according to their 
velocities measured in terms of that unit. 
Expressions for the accelerations of the air particles are found, viz. :— 
Along the radius ie 406 ate —V cos a(V cosa+U sin @)/r 
Perpendicular to the radius... Gee —Vsina(V cosa+U sin 6)fr. 
The time along the relative curve is found to be given by :— 
t—t, =A(A +B sin 6+C cos 4)r/U, 
where A= —(1+k’*)(1—A?+k’*)/k 
= —A(1-V°+#)/k 
C=a(1—a?+ k?) 
and k? = tan?a(1—A?). 
The coordinates of the path in space are then found to be 
x= Ut+r cos 6 
=[A(A+B sin 6+ C cos 6) + cos 8]7 + const 
y =r sin @ 
together with the equation for 7 in terms of 6. ; 
The particular case, studied by Dr. Shaw, where U=V and a=0 is then 
deduced, in the form 
(Yo— Y)(2Yo + 9)? = Syor*. 
3. The Distribution of Atmospheric Pressure in Canada. 
By R. F. Stuparr. 
4. On the Size of Hailstones observed during a Storm in Western Canada. 
By J. W. Surerey, B.A. 
The author took the opportunity of recording the size and shape of 
hailstones that fell during a recent storm in the foot hills of the Rockies, 
some of which were larger than hen’s eggs. At the centre of one hailstone 
a small black fly was found. 
5. Some Resulis of Stellar Parallax Investigations made at the 
Radcliffe Observatory, Oxford. By Dr. A. A. Rampavt, F.R.S. 
Within the last six years the astronomical equipment of the Radcliffe 
Observatory received an important addition in the shape of an equatorial instru- 
ment carrying two telescopes of 24 inches and 18 inches aperture respectively, 
the focal length of both being 22 feet 6 inches. A full description of the 
instrument will be found in ‘ Engineering’ for December 21, 1906. 
Preliminary observations haying shown the suitability of the instrument for 
work of high precision, it was determined to apply it to the investigation of 
stellar parallax, adopting Kapteyn’s photographic method. The immediate object 
of the research was to demonstrate the feasibility of a photographic ‘ Durchmus- 
terung’ for parallax extending to stars of the 13th or 14th magnitude. For 
this purpose nine regions of the sky were selected in consultation with Professor 
Kapteyn, and of these forty-six complete photographs, each consisting of twelve 
separate exposures, have been obtained. The work of measuring and discussing 
these plates is still in progress, but in this paper an account is given of some of 
the results already obtained. 
Five plates representing the region surrounding the star L1 5761 were sent to 
Professor Kapteyn and were measured and discussed by him at the Astronomical 
Laboratory, Groningen. This star is of magnitude 8:0, and its place for 19050 
