80 Reviews — Nicholson and Lydekker's Paleontology. 



By various experiments it appears that the coarseness of the 

 structure depends on, first, the thickness of the balsam heaped on 

 the plate (when thinly spread the tendency is for the structure to 

 be fine) ; second, the coarseness of the emery used in roughing the 

 surface of the glass (fine flour emery generally giving rise to almost 

 microscopic structure). 



The illustration given is from a photograph of an actual specimen. 

 The pumiceous structure, with its characteristic silky lustre, may be 

 obtained by taking Canada Balsam made brittle by evaporation, and 

 whilst in a soft condition stirred and beaten up with a thin strip of 

 metal previously made warm to prevent the cooling of the balsam, 

 until the soft mass is thoroughly permeated with air bubbles. It is 

 then taken in a lump and pulled out several times, when the lustrous 

 substance is obtained. This product resembles very closely the 

 Schiller Obsidian of the Caucasus. 



The above experiments were for the most part worked out in the 

 Geological Laboratory of the Normal School of Science. 



EEYIE "W" S_ 



I. — A Manual of Palaeontology fob the Use of Students, with 

 a General Introduction on the Principles of Palaeontology. 

 ByHENRY Alleyne Nicholson, M.D., D.Sc, F.G.S., etc., Regius 

 Professor of Natural History in the University of Aberdeen, 

 and Richard Lydekker, B.A., F.G.S., etc. Third Edition. 

 Re-written and greatly enlarged. In Two Vols. Royal 8vo. 

 pp. 1624, with 1419 Woodcut Illustrations. (William Black- 

 wood & Sons, Edinburgh and London, 1889.) 



THE contents of these two portly volumes fully bear out the 

 authors' statement in the preface as to the rapid advance of 

 palaBontological science within the last ten years. When compared 

 with the second edition issued in 1879, we find, notwithstanding the 

 employment of somewhat smaller type and leads, an increase of 

 554 printed pages, whilst the number of the illustrations is nearly 

 doubled. So great have been the changes and discoveries in the 

 science within the last decade, that it has been found necessary to 

 entirely rewrite and recast the whole; hence it has a just claim to 

 be considered as a new work. The great development in the 

 history of fossil Vertebrates within the last few years has also 

 made it almost impossible for any one not a specialist to treat this 

 branch of the science in a competent manner, and it is therefore 

 a decided advantage to find that in this edition the description of the 

 Vertebrates has been undertaken by Mr. R. Lydekker. 



Not only, however, do these volumes indicate a decided increase 

 in our knowledge of fossil organisms in recent years, but they also 

 furnish satisfactory evidence of the improvement which has taken 

 place in the character and methods of pala^ontological research, so 

 that, whatever may have been its deficiencies in the past, palaaontology 

 has now a just right to recognition as a separate department of 



