194 



Notes and Comments. 



RECORD YOUR PHOTOGRAPHS. 

 We have already referred in these columns to the excellent 

 work being accomplished by the Geolog'ical Photographs Com- 

 mittee of the British Association, guided by its secretary, Prof. 

 W. W. Watts. A third set of platinotype photographs, selected 

 from the committee's most valuable series, has just been issued 

 to subscribers, and exceeds in interest that of the two previous 

 issues. In it are several old friends, which are therefore 

 welcome. One of these is reproduced herewith, together with 

 the description thereof by Mr. G. W. Lamplugh. These alone 

 should convince photographers of the necessity of taking per- 

 m.anent record of objects of this character, and of the value 

 attached to the prints if sent to the Geological Photographs 

 Committee. It is to be hoped that the Geological Photographs 

 Committee of the Yorkshire Naturalists' Union will materially 

 assist the larger committee in its work during the coming year. 



PLUVIAL DENUDATION IN YORKSHIRE. 

 The most remarkable physical feature of the Yorkshire 

 Wolds is their ramifying system of streamless dales, floored 

 with the gravels of bygone water-courses. Under present 

 climatal conditions the ordinary rainfall is readily absorbed by 

 the much-jointed chalk, and the drainage is almost entirely sub- 

 terranean. But occasionally, when there is a rapid melting of 

 thick snows while the subsoil is still frozen, or when rain falls 

 so suddenly and so heavily that the soakage capacity of the 

 land is overtaxed, the ' dry bones ' of the dales are stirred by 

 brief floods that assert their ancient right-of-way, and play 

 havoc with the impediments which short-memoried man has 

 placed in their path. The photograph shows the effect of one 

 of these exceptional happenings in a dale three-quarters of a 

 mile w^est of Langtoft, an agricultural village in a wold valley, 

 six miles north of Driffield. On 3rd July 1892 a torrential rain 

 started cascades pouring suddenly down the slopes of the dale, 

 ripping gullies through the chalk-rubble and shaken rock, and 

 spreading a fan of detritus at the foot of the slope after the 

 manner of rain-storms in arid mountain lands, but fortunately 

 not very frequent in our country. The tempestuous flood then 

 swept along the bottom of the dale and wrecked the low-lying 

 parts of Langtoft, imperilling the lives of certain villagers and 

 actually drowning some of their pigs. Four years previously, 

 on 9th June 1888, there had been a similar though less destruc- 

 tive flood, by which the gullies shown in the photograph were 



Naturalist, 



