ON THE SEDIMENTARY DEPOSITS OF THE RIVER ONNY. 11 



they are not in a position to direct that the former investigation shall be 

 continued by the officers of the Geological Survey. 



" The investigation referred to was not made at the public cost ; and it 

 does not appear to My Lords that a special inquiry of this nature, involving 

 considerable additional expense, falls within the object for which the sum 

 voted by Parliament for the Geological Survey has been granted. 



" I am, Sir, 



" Your obedient Servant, 



" NoEMAj^- Macleod, 

 " Prof. Q. G. Stol-es, M.A., F.R.S., Assist. Secretary." 



Lensfield Cottage, Cambridge.'" 



After this reply, the Committee did not think that they could take any 

 further steps in the matter. 



G. G. Stokes. 



llOBERT HaRKNESS. 

 E. GODWIN-AUSXEN. 



Report on the Sedimentary Deposits of the River Onny. 

 By the Rev. J. D. La Touche. 



The principal rainfalls in the valley which supplies the waters of the Onny 

 during the past year, occurred from December 17th to 20th, January 6th 

 to 9th, 13th and 14th, February 1st to 10th, and March 1st to 4th. At 

 none of these dates did the river attain the height it has done on former 

 occasions. For this reason, and the long-continued droughts, the results of 

 these experiments have been rather barren. 



The accompanying Table shows that the relation of deposit to rainfall is 

 modified by many circumstances. As might be expected, the greatest quan- 

 tity is attained when a flood takes place after continued wet weather. Thus, 

 after the rains of last February, the floods of the 1st and 2nd of March were 

 followed by the largest amount of deposit observed in the year ; on this 

 occasion from 1318 lbs. per minute on the 2nd, to 2128 lbs. per minute on 

 the 3rd (that is, about 57 tons per hour), passed down. 



In considering these quantities, it must be remembered that the Onny is 

 a small stream : its width is 60 feet ; the area of the section where these 

 experiments are made is, at summer level, 92 square feet ; and the discharge 

 at a high flood amounts to about 80,000 cubic feet per minute. The area 

 of the Severn at summer level is 512 square feet ; and its discharge, under 

 similar circumstances, would probably be about 900,000 cubic feet per 

 minute. Assuming that the ratio of deposit in the water of the Severn were 

 the same as that observed in the Onny, no less than 1239 tons per hour of 

 solid matter would be carried by it in suspension past each spot. This, of 

 course, leaves out of account the pebbles and sand, which are occasionally 

 rolled along the bottom in great quantities. 



"Within the last year a gauge has been erected on the Severn, at Shrews- 

 bury, at the cost of the grant made by the Association. A register of the 

 floods has moreover been kept ; but as yet there has been some difliculty in 

 obtaining water for examination. This, it is hoped, may be done during the 

 ensuing year, as well as at Hereford, where a record is regularly kept of a 

 gauge on the Wye. 



