352 SECTIONAL TRANSACTIONS.—G. 
fishery and water supply, are referred to; and it is indicated how the 
knowledge of rainfall, flows and water levels will be a guarantee against 
developments which would be harmful to the amenities and legitimate use 
of the river and its water. 
The general scope of the water survey is outlined by a map of the catch- 
ment areas showing rainfall and physical characteristics. 
The methods of keeping records are outlined and the results, arrived at 
from these records, are illustrated by the diagram of a long and intense 
flood on the Inverness-shire Garry—the diagram showing clearly the 
correlation of rainfall, run-off and storage during the passage of the flood, 
and the important correlation of run-off and storage during the following 
dry period. ‘The flow gauging methods are briefly referred to, and the 
great value of systematic water level records at permanent and temporary 
stations is emphasised. 
AFTERNOON. 
Excursion to Banchory, Cairnton and Wood End House for river- 
gauging demonstration 
Wednesday, September 12. 
REPORT OF COMMITTEE ON STRESSES IN OVERSTRAINED MATERIALS (10.0). 
Prof. B. P. Haicu.—The lower yield point .in mild steel : measurement, 
specification and application in design (10.10). 
It is generally believed that considerable reductions in the weights of 
plates and rolled sections used in mild steel structures may be justified by 
accumulated advances in constructional technique, and particularly by the 
more general adoption of welding in lieu of riveting. As ameans to this end, 
affording a more reliable basis for the estimation of the actual strength of 
structures, the more general use of the so-called ‘lower’ yield point is 
recommended in lieu of the ultimate tensile strength. 
A few tests are described, and references are made to others, to show how 
the ‘ lower’ yield point is readily measured in mild steel, after plastic strain 
has commenced under a load that may be considerably greater. It is shown 
that the lower yield point value is more consistently reliable than the higher 
value more commonly quoted. 
A draft specification is submitted for consideration with a view to adoption 
by the standardising Institutions. It is suggested that this specification 
should be standardised for the use of those who may desire to use it, although 
it should not at present be substituted to replace the current specification 
of the higher yield point. 
Tests on welded joints in beams, and on welded high-pressure penstocks 
for the development of water power, are described in detail to show how the 
results observed in practice may be precalculated in a reliable manner and 
in exceedingly simple ways by using the lower yield point as a basis of 
calculation in lieu of the less reliable bases provided by the ultimate tensile 
strength or the limit of proportionality of the materials used. 
Mr. R. T. Mepp.—Aerial cableways (11.0). 
Definition. Origin of cableways in Aberdeen granite quarries and 
historical development. General consideration of the carrying capacity 
