230 TRANSACTTONS OF SECTION R. 



the meander being due ^^robably to the inflowing tributary in the first iustance. 

 The natural confluence of the Tyburn would seem to have been at the West- 

 minster bend, in the neighbourhood of "Whitehall. Once the stream had left 

 the gravel-capped plateau, vs'hose brink lies along Piccadilly and debouched into 

 the floodplain to the north of Buckingham Palace, its course may easily have 

 been diverted again and again by accident or intention. It may at one time 

 have joined the Wustbourne, or its waters may have been turned into one or 

 other of the numerous tidal creeks that drained the flats at low water. 



It does not seem possible to determine whether Thorney was a natural or 

 an artificial island, though the collection and plotting of excavation records in 

 suflicient number may eventually help us to s-ome conclusion. 



The course of the Tyburn in its upper and middle reaches, on the other hand, 

 may be easily traced, and can best be seen on the contoured map sketched from 

 the bench marks and ground levels given on the Ordnance Survey maps of 5 feet 

 to the mile. A street map, however, that gives minor lanes and alleys will 

 show the line the stream traced clearly enough to the observant eye, and its 

 valley is still fairly obvious to anyone who has the patience to track it out. 



From the geographical point of view the main interest in the site of West- 

 minster focuses round the work of tidal river and tributary stream in controlling 

 movement and settlement. 



3. Some of iJie Conditions Governing ilic Selection of an Aerial Route. 



By Colonel Towler, R.E. 



The purpose of this short .paper is to describe some of the peculiarities of 

 aircraft and their effect on the conditions aimed at in selecting an aerial route. 



An abstract of the requirements is as follows. The various items being con- 

 sidered individually, that route giving the best average fulfilment would be the 

 one selected. 



1. The first requirement is safety. 



Oversea flights in a land machine should, if possible, be not longer than half 

 the distance a machine can glide, without her engine, from the height at which 

 it is customary to fly. 



A suitable number of possible landing places available so that in the event of 

 engine failure a machine will, at any time, be within gliding distance of at least 

 one. Good and frequent meteorological information obtainable when required 

 so that risk of accident through sudden formation of fog and mist may be small. 



2. The second requirement is speed. 



The distance from the starting point to the destination should be the shortest 

 possible in order to economise in time and fuel. 



In the event of a forced landing the telegraph and railway should be near so 

 as to be available to forward news immediately of the position and requirements 

 of the aeroplane. Another machine can then be sent to complete the journey 

 with the passengers or merchandise, or again the necessary spare parts for the 

 repair of the machine which has landed cam be sent by air or rail. 



The requirements as to communication may in many instances be fulfilled by 

 the wireless telegraph or telephone installation carried in the machine. 



3. The third requirement is that the route shall have a number of distinctive 

 landmarks to help; the pilot in his navigation by recognitioiH of position. 



4. The Static Poioer of Melting Ice. By A. Trevor Battye, M.A. 



5. Crete. By A. Trevor Battye, M.A. 



FRIDAY, SEPTEMBER 12. 

 The following Papers were read : — 

 1. Colonisation in Africa. By Sir Alfred Sharp, K.C.M.G. 



