58 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



6. An Enquiry into the Suitability of Scottish-grown 

 Timber for Aeroplane and Pit-Prop Purposes. 



{With Plates.) 

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



The investigations into the physical properties of timber 

 grown in Scotland, described in this paper, were begun during 

 the war, at the time when, owing to the activities of German 

 submarines, it was becoming daily more difficult to keep up an 

 adequate supply of imported timber of a quality suitable for 

 aeroplane constructional work, and equally difficult to maintain 

 the necessary supplies of timber fit for pit-prop purposes in the 

 coal pits of this country. In the case of pit-prop timber, the 

 research was continued during the year 1919. If this country is 

 to be made self-supporting in regard to timber supplies for such 

 work as mining, it is essential to determine definitely whether 

 timber grown under ordinary conditions in Great Britain can 

 be converted into pit-props for use in the underground work 

 of coal-mines, of a quality and durability equal to that of the 

 imported material. The information which it was hoped to 

 obtain by this research would, it was thought, in a considerable 

 measure help to settle what kind of trees ought to be planted in 

 any area selected by the Forest Authorities for public or private 

 reafforestation. 



Aeroplane Work. 



This piece of work was necessarily one of urgency — time 

 could not be spent in preliminary investigations, a definite line 

 of work must be determined on, rigidly adhered to, and every 

 effort must be made to ensure that the results obtained in any 

 one day's testing operations should be strictly comparable with 

 those obtained on another day. It was, moreover, desirable to 

 carry out the tests determined upon on lines similar in all 

 respects to those which were being employed by other workers 

 who were investigating the suitability of timber grown in 

 England and Wales for aeroplane constructional work. The 

 tests adopted, therefore, were cross-breaking and crushing tests. 



Cross-breaking Tests. 



From each piece of timber sent to the laboratory for testing, 

 two or more specimens, each 48 inches long and 2 inches by 



