CORRESPONDING SOCIETIES. 585 



tlie inference of some people was that it would be of no use to attempt to 

 change the temperature artificially. 



Mr. W. M. Watts said that with regard to the mixture of lime with 

 clay in the sides of a dew-pond, he did not think that was necessary to 

 make them impervious ; but lime was frequently mixed with sandy 

 material to prevent it from slipping in the slope of a reservoir embank- 

 ment. With regard to the amount of dew, that could hardly exceed one 

 inch and a half per annum. 



Mr. James Barrowman was not aware that there were any dew-ponds 

 in Scotland. One point to be considered was whether the superficial area 

 of the pond had anything to do with its success. 



Mr. Hopkinson thought that it was of considerable importance in the 

 construction of these ponds that in the summer the receiving area was 

 usually more than double the evaporating area. 



Mr. G. P. Hughes said that dew-ponds were unknown in his district. 

 It occurred to him that they might prove useful in the future both in Aus- 

 tralia and in South Africa — dry countries where the dews were very heavy. 



The Rev. E. P. Knubley remarked that Wiltshire was a country of 

 dew-ponds. He suggested that all the Delegates should be supplied with 

 a list of questions, which they might attempt to answer by the date of the 

 next meeting. 



Professor Louis remarked that the exact composition of the water in 

 these dew-ponds was one of the essential points to be examined. 



Professor Potter said that in Warwickshire there were many ponds 

 which it was almost impossible to suppose could be fed by surface 

 drainage. In Suffolk there were a great number of small ponds which 

 formed the water-supply of villages, and were covered over and not 

 supplied by rain. In the south of Portugal there was a well-defined 

 wet season of short duration and a prolonged summer, in which no rain 

 fell at all. In that country there were many rock pools, and from the 

 scarcity of the rainfall and the excessive heat it was impossible to suppose 

 that these pools had been fed entirely by the rain. 



Professor Miall replied, and expressed the hope that the Corresponding 

 Societies would take up the subject and furnish additional information on 

 dew-ponds. 



The Chairman requested the Delegates to bring the subject before 

 their Societies. Mr. Vaughan Cornish remarked that he would see what 

 could be done in Hampshire and Berkshire to induce people to take the 

 matter up. The Rev. E. P. Knubley added that he would try to interest 

 some residents in Sussex. 



Section C. 



Mr. Monckton, representing Section C, drew attention to the labours 

 of two Committees who wished to obtain the co-operation of the Cor- 

 responding Societies in their work, the Geological Photographs Committee 

 and the Erratic Blocks Committee. As regards geological photographs, 

 the county of Yorkshire and the scientific Societies of Yorkshire were 

 pre-eminently first in the work up to the present time. The number of 

 geological photographs in the British Association's collection was 2,655, 

 the number received during the past year being 309, In this list he did 

 not include a certain number of duplicates and lantern slides. It was so 

 obvious that the taking of geological photographs was a work which could 

 be most usefully done by members of the Societies that he need say 

 nothing more on that head. Then the Committee for the Investigation of 



