92 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



8. An Enquiry into the Suitability of Scottish-grown 

 Timber for Aeroplane and Pit-Prop Purposes. 



{^Continuation.) 

 By Prof. T. Hudson Beare, M.Inst.C.E., D.L. 



On the completion of the compression tests of pit-props, 

 described in the earlier part of this paper {Transactions of the 

 Royal Scottish Arboricultural Society, vol. xxxvi. pp. 58-72), 

 it was decided to carry out a further series of tests of Scottish- 

 grown pit-props, as it was expected that it would be possible 

 to obtain, after peace had been re-established, rather better 

 representative samples of the different timbers than was possible 

 under the conditions existing in 1918. This additional work 

 was carried out mainly in 1920 and 192 1, though a few 

 additional tests have been made right up to the present year, 

 1924. 



As it is improbable that any further tests will be made for 

 some little time, I have thought it desirable to publish now 

 the 1919 and 1920 results, and at the same time to summarise 

 briefly the results of the whole series of tests and the conclusions 

 which can be safely drawn from this investigation. 



The pit-props tested in 1920 were mainly Scots pine, spruce, 

 and larch, grown on the estate of Finzean, Banchory, but in 

 addition a few props of Tsuga albertiana and Thuya gigantea, 

 grown at Murthly, and of Populus irichocarpa, grown at Dawyck, 

 Stobo, were also tested, and, finally, also for comparison 

 purposes, a set of foreign pit-props of Finnish red and white 

 wood, supplied by Messrs Love & Stewart. 



In these 1920 tests an endeavour was made to determine, 

 by counting the annual rings, the approximate age of the trees 

 from which the props had been cut; the foreign wood props 

 and those of Scots pine, spruce, and larch in this series of tests 

 were all sent to my laboratory with the bark removed, and were 

 therefore tested in this condition ; the other props of this series 

 were tested like those of the 19 18 experiments with the bark on. 



The props tested in 192 1 were nearly all soft woods and 

 included the following — Scots pine, larch, spruce, Douglas fir, 

 Weymouth pine and Thuya gigantea, and the forests in which 

 they were grown were scattered widely over Scotland. 



In this series of tests no attempt was made to determine the 

 age of the trees ; some were tested with the bark on the prop. 



