Ii6 Notes and Comments. 



1887), W. Middleton (1827), Giles Munby (1833) and Samuel 

 Hailstone (1859). Yorkshire naturalists are certainly grateful 

 to Mr. Wilkinson for his enormous work in making the botanical 

 treasures of the York Mustum available to students, and the 

 Yorkshire Philosophical Society is also no doubt glad to have 

 its Herbarium increased in value by the publication of the 

 list. We are personally gratified to learn that some remarks 

 of our own in ' Yorkshire's Contribution to Science ' were the 

 means of facilitating tke publication of the Catalogue. 



CHELLASTON GYPSUM-BRECCIA. 



At a recent meeting of the Geological Society of London, a 

 communication was read on ' The Chellaston Gypsum-Breccia 

 considered in its Relation to the Gypsum-Anhydrite Deposits 

 of Britain,' by Mr. Bernard Smith. This communication was 

 designed to clear up some of the ambiguities that have arisen 

 with regard to the actual mode of formation of the deposits of 

 gypsum in Britain — chiefly from the point of view of the field 

 observer. An attempt was made also to show the true rela- 

 tionship of the gypsum to the beds of anhydrite with which it 

 is sometimes associated. A description was given of a re- 

 markable breccia occurring at Chellaston in Derbyshire, and 

 its origin was discussed. Important occurrences of gypsum 

 in other parts of the country, as well as the alternative theories 

 as to their mode of formation, were then reviewed in the light 

 thus obtained. The remainder of the paper dealt mainly 

 with the possible interchanges between anhydrite and gj^psum. 

 The place and the function of the fibrous form of gypsum were 

 indicated, and a nomenclature suggested for certain isolated 

 masses of the mineral. 



CONCLUSION. 



(i) At Chellaston the gypsum was laid down as such, and 

 has suffered no appreciable alteration or addition since the 

 time of its original deposition and brecciation. There is no 

 evidence that the rock was every anhydrous. (2) By compari- 

 son with this deposit, and also by independent evidence, it 

 seems probable that most of the important beds of gypsum 

 in the country were laid down as gypsum, and have behaved 

 throughout as stratified deposits. (3) When anhydrite is 

 present, the evidence favours the view that it is original, 

 and was deposited in a stratiform manner in sequence with 

 gypsum. (4) Microscopic evidence shows that there has 

 been, in some cases, an alteration of anhydrite into gypsum 

 where the two minerals were in original juxtaposition ; this 

 alteration, however, is considered to have occurred at, or 

 immediately after, the time of deposition, and to be confined 

 to the existing plane of contact of the two minerals. 



Naturalist, 



