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Proceedings of the British Association. 



the upper as in the lower regions. — 2. Longitudinal and vertical strata. 

 Dr. Stark stated that this structure had been described by Griiner 

 in 1760, by Desmarest in 1779, Scoresby in 1824, and other authors, 

 and during the last winter had been claimed as a new discovery by 

 Prof. Forbes, who styled it ribboned or banded structure. These 

 layers he described as always of great tenuity, forming planes more 

 or less vertical, but always parallel with the length of the glacier or its 

 retaining walls. The explanation of this structure offered by Dr. Stark 

 is as follows: — During the spring and summer months it is probable 

 that glaciers advance from 1 \ to 3 feet daily, and as the valleys oc- 

 cupied by them generally widen as they recede from the higher regions, 

 every movement would leave a space between them and their con- 

 taining walls ; these fissures would continually fill up with fresh 

 snow and ice, increasing the breadth of the glacier, and forming a 

 new series of vertical planes. The frequent occurrence of mud, gravel, 

 and fragments of rock in the same planes, was considered by Dr. Stark 

 to be much in favour of this explanation of their origin. This struc- 

 ture, he remarked, was likely to be found wherever pillars and needles 

 of ice were met with, since fissures and crevices generally divided 

 glaciers transversely; and in passing over rough ground, the unequal 

 pressure on a combination of transverse fissures and longitudinal 

 lamellae would break up the ice into vertical prismatic columns. — 3. 

 Horizontal combined with longitudinal and vertical strata. Although no 

 such combination as this had hitherto been described, Dr. Stark thought 

 it must exist. Horizontally stratified ice was confined to elevated 

 regions, where the thickness of glaciers was three or four times greater 

 than in lower valleys. Dr. Stark inferred that these beds gradually 

 wasted away as the glacier descended, until only the lower, or ver- 

 tically stratified, portion remained. — 4. Inclined strata. This struc- 

 ture Dr. Stark endeavoured to explain as one superinduced, after 

 the accidental destruction of the lines of stratification which former- 

 ly existed. In conclusion, Dr. Stark observed, that all the above forms 

 of stratification might be expected to occur in the extent of a single 

 glacier. 



Dr. Richardson observed, that snow constantly disappeared in great 

 quantities without melting ; in dry frosty air, with a temperature below 

 zero, it would disappear rapidly by insensible evaporation. The pris- 

 matic form of ice, which occurs on lakes where it has attained a thick- 

 ness of six or eight feet, takes place only in the spring, when it begins 

 to melt ; the particles were considered to undergo a new arrangement 

 when the temperature of the mass was elevated to the melting point.— 



