S53 



tlie subject of tbe deposits of rivers. Sir Charles then expressed an opinion 

 as to the great advantages resulting to science from the observations of 

 members of NaturaUsts' clubs, and hoped that they would proceed with their 

 enquiries and carefully record the results. In this idea Mr. Symonds heartily 

 concurred, and urged the members present to diUgently examine the pheno- 

 mena of Nature for themselves and thus advance the interests of science. 



Mr. E. Lees wished to ask a question as the deposits made by rivers in 

 the present day, which seemed more unequal now than formerlj'. He had 

 noticed that the meadows on the banks of the Severn near AVorcester an 

 allu\-ial deposit of between sLx and seven feet, but since these meadows had 

 become permanent pasture covered with grass they showed no appreciable ad- 

 dition except on the bank itself, and the great mass of muddy deposit was 

 carried down into the sea. 



The President in reply to this said that the process of deposit described 

 gradually caused its own cessation, as the low grounds adjacent to rivers were 

 raised by successive films of deposit, so they became elevated above ordinary 

 floods, and were covered with water more and more rarely, until at last a point 

 was reached when they ceased to be flooded at all. The alteration of the beds of 

 rivers which, at aU events in the upper parts of their course, were slowly cut 

 down deeper and deeper, contributed to the same cessation of deposit. He had 

 recently examined the water of the Kenvy dm-ing a high flood, and found that 

 it contained rather more than two giains of matter in suspension in an imperial 

 liint, or about one part in four thousand. The quantity of water flowing at the 

 time was estimated at 36,800 tons per hour, thus this small brook was carrying 

 down during flood nine tons of solid matter per hour, or at the rate of more 

 than 200 tons per day. The greatest proportion of solid matter which was 

 observed by Mr. Latouche was much higher than this, or about one part iu 1700. 

 Tills probably arises from the difference of soils, as a larger quantity of the fine 

 Silurian mudstones would be carried in suspension than of the coarser deposits 

 of the old red sandstone. 



'Mi. Cuelet said that he would explain the fact stated by Mr. Lees in 

 this way. The deposit brought down by the Severn was filtered by the grass 

 now covering the meadows and stopped upon the banks, so that the banks of 

 the river were elevated above the adjacent ground, and he knew instances where 

 the banks of a stream were raised as much as two feet by this action, and 

 even the bottom of a stream became higher than the land beyond its banks. 



Mr. LiGHTBODT considered that a deposit was stiU actually made upon 

 meadows when the stream overflowed its banks, but this was absorbed by the 

 roots of the grass which rose higher upon the deposit. Obstructions to the 

 free course of streams arose near their mouths, and here consequently was the 

 greatest amount of debris. 



Mr. John Lloyd stated that he had observed the way in which the Po 

 had accumulated soil upon its banks in Italy, so that the banks of that river 



