50 REPORT— 1860. 



friability and regelation have been shown by the experiments of Professor Tyndall 

 to be sufficient (the requisite force " a tergo " being supposed) to account for its 

 crushing its way through contractions in its channel, and reconstructing itself at the 

 bottom of ice-cataracts. Now such a glacier, if it be supposed penetrable to external 

 heat as lead is, could not but descend as lead does. In its descent portions of it 

 would be thrust forward and compressed, and others would be dragged behind and 

 crevassed. The melting of the lower part of such a glacier would favour its descent 

 as compared with the lead whose mass remains unchanged. All these conditions 

 might, however, be influenced by variations in the form of its channel and the incli- 

 nation of its bed. Its motion would be like that of a snail clinging, but descending. 

 The whole question, however, depends upon the penetrability of the glacier to 

 external heat. On this point we have the high authority of Professor Forbes, 

 founded on three series of observations on the motions of the Mer de Glace and the 

 Glaciers des Bossons and des Bois. Of these observations, made in the summers of 

 1842 and 1844, he has recorded the results in his 'Travels in Savoy' (2nd ed. 

 p. 141), and in his recent work entitled ' On the Theory of Glaciers ' (p. 131) ; and 

 he has compared them with the mean daily temperatures of the air as recorded at 

 Geneva and the Great St. Bernard. He has, moreover, represented the relation 

 between the average daily motions of these glaciers, and the average daily tempera- 

 tures of the air at the corresponding periods by means of diagrams, which it is im- 

 possible to look at, however cursorily, without being struck with the fact (not to be 

 better expressed than in the words of Mr. Forbes himself), that they establish a 

 " close relation between the mean temperature of any portion of the year, and the 

 velocity of the glacier corresponding to it*." Moreover, it is not only on the sur- 

 face of the glacier that this relation may be considered to have been observed. The 

 glacier moves with different velocities at different depths ; but all are related to its 

 surface motion, so that the influence of variations of temperature, if felt on its sur- 

 face, must penetrate throughout its depth. Being dilatable as lead is (but in a 

 higher degree), and being thus shown to be sensible to variations of temperature 

 throughout its mass, it cannot but descend as lead uuder the like circumstances does. 

 Every variation of temperature, however slight, cannot but produce a corresponding 

 descent, and such small variations, often enough repeated, might produce a descent, 

 however great, even although at each change the glacier returned to the same tem- 

 perature. The oscillation of the heat backwards and forwards is all that is required. 

 For the purpose of this argument, the fact that a relation exists between the motion 

 of a glacier and the external temperature is all that is required. It is not necessary 

 to enter on a discussion of the causes out of which that relation arises. 



On Meteorological Observations for 18.59, made at Huggate, Yorkshire, East 

 Riding. By the Rev. T. Rankin. 



This communication was in continuation of similar observations and general 

 remarks furnished, by the same author, to the Association for upwards of twenty 

 vears. 



On Thermo -barometers, compared with Barometers at great Heights. 

 By M. R. de Schlagintweit. 



M. Robert de Schlagintweit communicated some of the results which he had de- 

 duced from comparisons of the boiling-point with direct barometric readings. These 

 observations, taken by his brothers and himself during their journeys in India, the 

 Himalaya, &c, at various heights and different periods, were chiefly made to test by- 

 direct experiments the correctness of the tables of the boiling-point of water corre- 

 sponding to barometric pressure, of which the latest and the most detailed ones are 

 those of Magnus, Regnault, and Moritz. 



Direct observations had been previously made in India, particularly by Colonel 

 Sykes ; in America, Mr. Wisse made such experiments up to 14,000 feet; in High 

 Asia, Messrs. de Schlagintweit had occasion to carry on such observations up to 

 heights exceeding 18,600 feet. 



A resulting Table of comparison was presented, an examination of which showed 



* Forbes, Theory of Glaciers, p. 130. 



