321 



feature in t!ie results is, tluit the orest of tlie wave travels with 

 the same velocity, whether at the edg^es or in the centre of the 

 canal, provided the wave be of the simplest form. In a triang^i- 

 lar canal, for instance, this is true. This result would, at first 

 sight, appear to be utterly at variance with tide-observations; 

 but the discrepancy will be less striking' when it is remembered 

 that observations of this kind are for the most part made in bays, 

 or, as it were, small detached channels, and that consequently 

 the times of high water registered are rarely those corresponding 

 to the great tidal wave, but to a secondary to it, following at a 

 considerable interval. However this be, Mr Russell states, that 

 the conclusion coincides exactly with his experiments. Another 

 result obtained in this section is, that the square of the velocity 

 of transmission in a triangular canal is one-half that in a rect- 

 angular canal of the same greatest depth. This result was ob- 

 tained in the former memoir, and agrees well with experiment. 

 On adding further to the hypothesis, that the continuity extends 

 to small distances below the surface, we find, as the result of 

 an accurate solution (no longer using an approximation), that 

 the approximate result is too great or too small, according as 

 the breadth from the vertical, though the lowest point to the 

 edge, is greater or less than the depth. The crest of the wave 

 rises rapidly towards the shallow part of the fluid. The last sec- 

 tion is occupied in deducing the circumstances of initial motion 

 of a fluid. 



3 Anah'sis of Berg-Meal from Umea Lapmark. By Dr 



Traill. 



Professor Traill gave an account of the composition of a sub- 

 stance brought under the name of Bcrg-Mcal from Swedish Lap- 

 mark by Mr Laing in 1838. It was found just under a bed of de- 

 cayed mosses, forty miles above Degersfors, in Umea Lapmark. 

 When examined by the microscope, it was found to consist of several 

 species of minute organic remains, which Ehrenberg has consi- 

 dered as the siliceous skeletons of infusoria; the largest measured 

 from 0.006 to 0.0005 of an inch. On analysis, Dr T. obtained 

 22 per cent, of organic matter, entirely destructible by a red heat ; 

 and he found the snow-white residue, which still retained the mi- 

 croscopic forms, to consist of 71.1.3 of silica, 5.31 alumina, and 

 0.15 oxide of iron. He considers the organic matter and the si- 

 lica, as the essential ingredients, and the others probably as ac- 

 cidental. As a mixture with food, the quantity of organic mat- 



