PEOCEEDINGS 
OF THE 
ROYAL SOCIETY OF EDINBURGH. 
VOL. XV. 1887-88. No. 127. 
Monday, 20th February 1888. 
Sir william THOMSON, President, in the Chair. 
The following Communications were read : — 
1. Preliminary Note on the Duration of Impact. By 
Professor Tait. 
The results already obtained were got by means of a roughly 
made apparatus designed for the purpose of testing the method used, 
so that only a single instance, to show their general character, need 
now be given. When a wooden block of 10 lbs. mass fell through a 
height of 18^ inches on a rounded lump of gutta-percha, the time of 
impact was found to be somewhere about O’OOl sec., and the co- 
efficient of restitution was 0‘26. 
As the principle of the method has been found satisfactory in 
practice, new apparatus is in course of construction, which will 
enable me to use a fall amounting to 10 feet at least. It is proposed 
to make a series of experiments on different substances, Avith great 
varieties of mass and of speed in the impinging body. 
2. A Bathymetrical Survey of the Chief Perthshire 
Lochs, and their relation to the Grlaciation of the 
District. By James S. Grant Wilson, Esq., H.M. 
Geological Survey. Communicated by Dr Archibald Geikte, 
F.R.S., Director-General of the Geological Survey. 
VOL. XV. 1/10/88 
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