330 



ciling the discrepancies of the curve which represents this inequality 

 for different places ; discrepancies which have hitherto been a source 

 of much perplexity. These differences in the semimenstrual inequa- 

 lity are shown by the author to be consequences of peculiar local cir- 

 cumstances, such as the particular form of the coast, the distance 

 which the tide wave has travelled over, and the meeting of tides pro- 

 ceeding in different directions; and he traces the influence of each of 

 these several causes in producing these differences. A diurnal dif- 

 ference in the height of the tides manifests itself with remarkable con- 

 stancy along a large portion of the coast under consideration. The 

 tide hour appears to vary rapidly in rounding the main promon- 

 tories of the coast, and very slowly in passing along the shores of the 

 intervening bays; so that the cotidal lines are brought close together 

 in the former cases, and, in the latter, run along nearly parallel to 

 the shore ; circumstances which will also account for comparative 

 differences of level, and of corresponding velocities in the tide stream. 

 The author intends to prosecute the subject when the whole of the 

 returns of these observations shall have undergone reduction. 



A paper was also read, entitled, " Copies of Registers of the Ther- 

 mometer kept at Alford, Aberdeenshire." By the Rev. James Far- 

 quharson, F.R.S. 



The observations recorded in these tables were made at 9 h I5 m 

 a.m., and at 8 h 30 m p.m., each day of the year 1833 ; and the 

 highest and lowest temperatures in each month observed from the in- 

 dications of Six's thermometer. The author remarks that the differ- 

 ences between the temperature of the morning and evening hours of 

 observation were greatest, on an average, during clear weather ; that 

 is, when the radiation of heat from the ground is greatest. 



The reading of another paper, by the same author, entitled " On 

 the Ice, formed under peculiar circumstances, at the bottom of running 

 Water," was commenced, but not concluded. 



SIR BENJAMIN COLLINS BRODIE, Bart., Vice-President, in 



the Chair. 



The reading of a paper entitled, " On the Ice, formed under pecu- 

 liar circumstances, at the bottom of running Water." By the Rev. 

 James Farquharson, of Alford, F.R.S., was resumed and concluded. 



The ice, which is frequently observed to collect at the bottom of 

 streams and rivers, differs in appearance from that which is formed at 

 the surface; for, instead of assuming the shape of solid glass-like 

 plates,it has more the appearance of aggregated masses of snow, and is 

 composed of small crystals of ice adhering together irregularly, either by 

 their sides or angles. Rivers are sometimes so choked up by accumu- 

 lations of ground-ice of this description, that they are not only impeded 

 in their course, but also raised considerably above their banks. While 

 in this state, a slight change in the weather will frequently occasion 

 the complete disengagement of this ice from the bottom ; so that, in 

 a very short space of time, the river returns into its natural channel ; 



