32 Reviews — Pattisons Slate and Slate-quarries. 



of the new forms which they present. It is important, however, — let 

 us say it in passing, — never to forget, in this study of the evolution of 

 types, that the consequences of an observed fact can be only relative, 

 seeing the insufficiency of researches and the small extent of the 

 field of observation. We can well say, for example, that until now, 

 no genus of the family of the Spatangidce has made its appearance 

 before the Cretaceous epoch; but can we know if the attentive 

 exploration of some Jurassic formations shall not at last reveal the 

 existence of some precursor type? The frequency of similar dis- 

 coveries ought to put the serious observer on his guard, and warn 

 him that he ought always to be ready to modify his theories in pro- 

 portion as the exact observation of some new fact comes to demon- 

 strate to him that they were preconceived." 



In the Livraisons before us the authors have described and figured 

 the Jurassic Cidaridce, embracing the genera Cidaris, Bahdocidaris, 

 Polycidaris, and Pseudocidaris. The description of each species is 

 clearly and accurately made, and their affinities and differences 

 succinctly pointed out. The tables of synonyms, so important to a 

 correct knowledge of fossil species, are compiled with great care and 

 much discrimination. 



The plates are good, but several of them have not been well 

 printed, and are woolly and indistinct. The want of a clear definition 

 in the details of fossil Echinidae is a great defect in figures to which 

 constant reference must be made, as standards of authority for the 

 characters of forms that are often only found in a fragmentary 

 state. Perhaps the future plates will be free from this defect, which 

 is more the fault of the printer than the artist. 



The work reflects very great credit on its authors, and we 

 heartily wish it all the success its scientific merits so justly entitle 

 it to. T. W. 



n. — Slate and Slate Quarries, Geologically and Commercially 

 Considered. By S. E. Pattison, F.G.S. London, 1869. 



SLATE is an article alike interesting to the geologist and econo- 

 mist, whether we regard with the one its mode of formation, 

 or with the other the various uses to which it is applied. It is an 

 essential adjunct to modern architecture; for although occasionally 

 the red or glazed tile may be suitable for a certain style of building, 

 the blue or green slate is certainly in the ascendant. From its 

 lightness, imperviousness, and comparative durability, slate has to a 

 great extent superseded the thatch, wood, and tiles ; and even in the 

 central counties of England, since the introduction of railways, it 

 has largely replaced the more cumbrous Stonesfield and Collyweston 

 flags, which, from their weight, required a stronger wood support. 

 Slates, however, were used in the old fortresses of Wales, as well as 

 in the castle of Angers, Brittany, built in the time of the Planta- 

 genets, both near the centre of production. 



The pamphlet before us is a reprint of a series of papers con- 

 tributed by Mr. Pattison to the Mining Journal under the following 

 heads : Composition and structure ; Geology and Paloeontology of 



