188 REPORT — 1873. 



Report of the Committee, consisting of Professor Ramsay, Professor 

 Geikie, Professor J. Young, Professor Nicol, Dr. Bryce, Dr. 

 Arthur Mitchell, Professor Hull, Sir B,. Griffith, Bart., Dr. 

 King, Professor Harkness, Mr. Prestwich, Mr. Hughes, Rev. 

 H. W. Crosskey, Mr. W. Jolly, Mr. D. Milne-Holme, and Mr. 

 Pengelly, appointed for the purpose of ascertaining the existence 

 in different parts of the United Kingdom of any Erratic Blocks or 

 Boulders, of indicating on Maps their position and height above the 

 sea, as also of ascertaining the nature of the rocks composing these 

 blocks, their size, shape, and other particulars of interest, and of 

 endeavouring to prevent the destruction of such blocks as in the opi- 

 nion of the Committee are worthy of being preserved. Drawn up by 

 the Rev. H. W. Crosskey, Secretary. 



The Royal Society of Edinburgh has appointed a Committee for the special 

 examination and description of Boulder or Erratic Blocks in Scotland ; and it 

 wiU therefore not be necessary for this Committee to include Scotland in its 

 investigations. 



Throughout England and Wales boulders and groups of boulders are 

 scattered, among which the work of destruction is constantly going on. 

 Groups of boulders are removed from the fields and built into waUs ; krge 

 boulders are frequently blasted ; and during these operations the signs of ice- 

 action are either rendered obscure or entirely removed. 



The geological importance, however, of obtaining the exact facts respecting 

 the distribution of travelled boulders is increasing with an extended knowledge 

 of the very complicated character of the phenomena of the glacial epoch. The 

 dispersion of boulders cannot be traced to one sbvjJe period of that great epoch. 



Prof. Ramsay has pointed out that transported blocks have travelled in 

 some instances over land higher than the parent beds from which they 

 have been derived, thus affording support to the theory that oscillations of 

 the land took place during the one great glacial period, which would neces- 

 sai'ily be accompanied by a scries of dispersions of boulders*. 



The distances of the boulders from the rocks from which they were de- 

 rived, the heights over which they have passed and at which they are found, 

 the matrix (if any) in which they are imbedded, whether of loose sand, 

 gravel, or clay, will form elements in determining at what period in the gla- 

 cial epoch their distribution took place. 



As the dispersion of boulders cannot be traced to one single period, 

 neither can it be referred to one single cause. 



The agency of land-ice, the direction in which icebergs would float during 

 the depression of the land, the power of rivers in flood to bring down 

 masses of floating ice, must be taken into account. 



It will not be the office of this Committee to oifer theoretical explanations, 

 but to coUect facts, although the bearing of these facts upon debatable geo- 

 logical problems may from time to time be not unjustly indicated. 



WTiile the dispersion of boulders can neither be traced to one single 

 period nor referred to one single cause, in some cases boulders distributed at 

 different periods and by different causes may have become intermixed. This 

 possibility, of course, largely adds to the complexity of the problems in- 

 volved, and to the difficulty of assigning to various isolated boulders and 

 groups of boulders their definite place in a great series of phenomena. 



The following circular has been distributed by the Boulder Committee of 

 the Royal Society of Edinburgh : — 



* Quart. Jouri). Gcol. Soc. toI. xiix. p. 360. 



