42 PROCEEDINGS OP THE GEOLOGICAL SOCIETY. [May 1 894,. 



and condolence with Mrs. Tyndall on the occasion of her husband's 

 death. 



It is not for us to consider the work of Tyndall as a physicist, 

 though it will be readily conceded that his powers as a scientific 

 expositor have hardly ever been equalled. Although he joined this 

 Society in 1868, it cannot be said that he ever took any active part 

 in the study of geology, nor has he ever contributed a paper to our 

 publications. But there have been certain problems more or less 

 connected with geological science to which he turned his ever active 

 mind, and to which brief allusion may be made, though these relate 

 to work achieved long ago. A notice of Tyndall's ideas on the 

 subject of slaty cleavage may be found in the introduction to his 

 famous work, ' The Glaciers of the Alps,' first published in 1860. 

 Well-nigh forty years have elapsed since that memorable visit to the 

 Penrhyn Slate Quarries, where his interest was aroused by what he 

 saw of the phenomena of slaty cleavage. He tells us he there found, 

 on enquiry, that the subject had already attracted the attention 

 of three English writers, Prof. Sedgwick, Mr. Daniel Sharpe, and 

 Mr. Sorby. Through Sedgwick he learned that cleavage and strati- 

 fication were things totally distinct from each other, but he was 

 obliged to disagree with his learned preceptor on the point that 

 slaty cleavage is of the same nature as crystalline cleavage. Tyndall 

 was not long in giving his adhesion to the mechanical theory, 

 and he justly remarked that science was indebted to Sharpe and 

 Sorby for the prime facts on which that theory rests. In another 

 department Tyndall's glacier work has been of great service to 

 geologists for the last five and thirty years, though not in itself 

 devoted, to any considerable extent, to the solution of geological 

 problems. He is credited with a belief that glaciers were possessed 

 of considerable excavating power, contrary to doctrines which have of 

 late prevailed. Nevertheless the whirligig of time brings old fashions 

 back again, and thus it comes to pass that the lake-basin theory has 

 lately had some able advocates. Tyndall also took an interest in 

 the subject of the Parallel Roads of Glen Roy, and was a supporter of 

 Jamieson's glacier-dam theory, though he never took any trouble 

 to ventilate these opinions in the geological literature of the day. 



The Rev. Charles Pbitchaed, F.R.S., Professor of Astronomy in 

 the University of Oxford, was born about the year 1810. He 

 graduated at St. John's College, Cambridge, where he took his degree 

 as fourth wrangler, being also a Fellow of his College. Por many 



