eS ee 
ON THE TEACHING OF ELEMENTARY MECAANICS. 99 
as E=14 mv”, or F=mdv/dt, in any consistent system of units whatever. 
They should learn that for certain purposes the C.G.S. system of units 
is convenient, and for certain other purposes the units employed by 
British engineers may be convenient ; they should not be dominated by 
any system, but able to use them all. The powndal and other such 
educational conveniences should be used as auxiliary units only, final 
results being expressed in units to which practical people are accustomed, 
so as to be generally intelligible. 
21. Atwood’s machine should be regarded as a means of illustrating 
the laws of motion, and not as an accurate method of finding g. 
22. With the idea of preventing the notion that acceleration is always 
uniform, and having regard to the importance in physics of simple 
‘harmonic motion, it-is advisable to consider such motion and the 
pendulum at an early stage. 
23. Easy problems on the motion of a fly-wheel should form part of 
a course on elementary mechanics. 
24. Centrifugal force should never be dealt with as if applied to 
the moving body, so as to reduce an essentially kinetic problem to a 
spuriously statical one. It is a force exerted by a curvilinearly moving 
body on its constraints. 
Investigation of the Upper Atmosphere by means of Kites in co-opera- 
tion with a Committee of the Royal Meteorological Society.—Sixth 
Report of the Committee, consisting of Dr. W. N. SHaw (Chairman), 
Mr. W. H. Dives (Secretary), Mr. D. ArncuipaLp, Mr. C. VERNON 
Boys, Dr. R. T. Guazesroox, Dr. H. R. Mitty, Professor A. 
Scuuster, and Dr. W. Watson. (Drawn up by the Secretary.) 
Meetines of the Joint Committee were held on November 13, 1906 ; 
also on January 24, May 9, May 23, and July 5, 1907. 
Observations have been made at Glossop Moor by Mr. J. E. Petavel, 
F.R.S., whose report on the subject is appended. 
The Committee have had under consideration a circular sent out by 
Professor Hesgesell, the President of the International Aéronautical 
Commission. In it he asks for the co-operation of England in a special 
series of kite and balloon ascents, and the Committee have arranged for 
some ascents, in addition to those undertaken by the Meteorological 
Office, on the specified days. 
At the meeting of the Joint Committee held on May 9 it was 
suggested that the British Association Committee should ask for re- 
appointment and for a grant of 25]. 
Glossop Moor Kite Station (Peak District). Report for the Session . 
1906-1907. Ay J. E. Peraven, £.2.8. 
This kite station was established in the spring of 1906 by Mr. G. ©. 
Simpson. 
The necessary winding gear was purchased by aid of a grant from the 
Royal Meteorological Society ; the other initial and current expenses have 
been defrayed by the Manchester University. 
During the present session some sixty successful ascents have been 
made, Messrs. T. V. Pring and W. A. Harwood having kindly acted as 
voluntary assistants. 
H 2 
