ON THE STRUCTURE OF CRYSTALS. 337 



It is true that by placing suitable bodies (molecules endowed with 

 certain symmetry) at the nodes of a space-lattice all the properties of a 

 crystal may be accounted for, but there seems no sufficient reason for 

 limiting the problem in this manner. The material occupying the 

 Fundamentalbereiche of Schonflies, or represented by a generalised point- 

 system, may always be supposed grouped about the nodes of the underlying 

 space-lattice if required, so that what were at first regarded as so many 

 units come to be the parts of a single composite unit ; but in some cases 

 the latter, like some of Haiiy's molecules sonstracfives, must be a mere 

 geometrical fiction. 



Until we know more about tlie units of which the crystal really con- 

 sists, there will necessarily be speculation as to whether the units are 

 situated at the most general sorts of homologous points in a given type, 

 or whether they are symmetrical bodies situated at the singular points ; 

 whether they are all of the same soi't or of more than one sort. 



It is proposed to consider in a subsequent report some of the mechanical 

 and physical conceptions which have been employed in discussing the 

 possible structure of crystals, and the definite structures recently ascribed 

 to certain substances.' 



The Movements of Underground Waters of North-ivest YorJcshire.— 

 Second Report of the Committee, consisting of Professor W. W. 

 Watts (Chairman), Mr. A. R. Dwerryhouse {Secretary), Pro- 

 fessor A. Smithells, Rev. E. Jones, Mr. Walter Morrison, 

 Mr. G. Bray, Rev. W. Lower Carter, Mr. W. Fairley, Mr. 

 P. F. Kendall, and Mr. J. E. Marr. 



The Committee are carrying out the investigation in conjunction with a 

 committee of the Yorkshire Geological and Polytechnic Society. 



The work of investigating the flow of underground water in Ingln- 

 boro', described in the report presented to the Association at the 

 Bradford meeting, was resumed \\y the Committee on November 10, 

 1900, when it was determined to study the underground course of a small 

 stream known as Hard Gill. 



This stream rises, on the south side of Ingleboro', in a spring at 

 1,600 feet above the sea, and flows for a distance of about half a mile 

 over boulder clay. 



It then reaches the bare limestone and commences to sink near the 

 eastern corner of the croft at Crina Bottom. 



In wet weather the stream is not entirely absorbed at this point, but 

 flows on past the house at Crina Bottom, and enters the rock at Rowan 

 Tree Hole (Rantree Hole on 6-in. map). 



At the time of the experiments the water of Hard Gill was entirely 

 absorbed between the point where the 1,200 feet contour crosses the 

 stream and the eastern corner of the croft, and consequently the investi- 

 gation of Rowan Tree Hole, the primary object of the excursion, had to 

 be abandoned. 



It was found, however, that the bulk of the water was absorbed at 

 the point where the 1,200 feet line crosses the stream, and consequently 



' This relates to work published by Mallard, Liveing, Fedorow, Kelvin, Wulff, 

 Barlow, Muthmann, Tutton, Sollas, Goldschmidt, Viola, and others. 



1901. Z 



