MATERIAL PREFERRED FOR STONE IMPLEMENTS. 63 



a period." Part, at least, of this evidence will be found in the 

 following pages ; and though it is true that much of it has 

 been obtained since our accomplished countryman published 

 the work from which I have just quoted, yet he has recently 

 repeated his previous statements in a lecture delivered at 

 Leeds. 



Our knowledge of this ancient period is derived princi- 

 pally from four sources, to the consideration of which I 

 propose to devote the four following chapters ; namely, 

 the tumuli, or ancient burial-mounds, the Lake habitations 

 of Switzerland, the Kjokkenmoddings, or shell -mounds, 

 of Denmark, and the Bone- Caves. There are, indeed, 

 other remains of great interest, such, for example, as the 

 ancient fortifications, the "castles" and "camps" which 

 crown so many of our hill-tops, and the great lines of 

 embankment, such as the Wansdyke, which cross so many 

 of our downs, where they have been spared by the plough ; 

 there are the so-called druidical circles, and the vestiges 

 of ancient habitations ; the " Hut-circles," " Cloghauns," 

 "Weems," "Picts' houses," etc. The majority of these 

 belong, however, in all probability, to a later period ; and 

 at any rate, in the present state of our knowledge, we can- 

 not say which, or how many of them, are referable to the 

 Stone age. 



As far as the material is concerned, every kind of stone, 

 which was hard and tough enough for the purpose, was 

 used in the manufacture of implements. The magnificent 

 collection of celts at Dublin has been specially studied, from 

 a mineralogical point of view, by the Rev. S. Haughton, and 

 the results are thus recorded by Wilde.* 



" Of the better qualities of rock suited for celt-making, 

 the type of the felspathic extreme of the series of trap rocks 



is the pure felstone, or petrosilex, of a pale blueish 



* Catalogue of the Royal Irish Academy, p. 72. 



