134 The Scottish Naturalist. 



more recent developments of our knowledge of the geological 

 phenomena of mountain districts. But they agree precisely with 

 the results which have been already worked out by extra-British 

 investigators. The stratigraphy of the North-west Highlands, as 

 I have more than once suggested, is precisely of the same character 

 as that so admirably described and illustrated by Heim * in his 

 magnificent work upon the Alps of Central Switzerland. The 

 metamorphic phenomena of the north-west, too, are identical with 

 those so minutely detailed and photographed in Lehmann's most 

 valuable work on the metamorphic rocks of the Saxon " Erzgebirge. 

 Continental geologists, British amateurs, and the officers of the 

 Geological Survey are now at one and the same point. They 

 stand together on the shore of a new world of geological discovery, 

 full of the richest promise." 



K E V I E W. 



THE LOGIC OP DEHNITIOff. 

 By Rev. WILLIAM L. DAVIDSON. 



Though Logic as a subject of special study hardly falls within 

 our ken, yet we cannot pass this work in silence. 



The whole book well repays careful perusal, but to biologists 

 the chapters of most value are those upon biological classification 

 and definition. Mr. Davidson looks at these subjects from the 

 side of the logician, but with an intelligent appreciation of the 

 special conditions under which biologists work out their problems, 

 and of the requirements that must be fulfilled to meet these special 

 conditions. From this standpoint he detects and exposes the many 

 defects that disfigure even the best works on the sciences of Botany 

 and Zoology, faults so great that when our attention is directed to 

 them we can but wonder that they could have been overlooked in 

 even the worst manuals, and yet that are proved fully by examples 

 from the most esteemed works in these sciences. Among these faults 

 in classification we are forced to recognise carelessness, inaccuracy, 

 defect, redundancy, and mention of characters under wrong grades ; 

 while in Defifiition we have pointed out to us loose and vague (or 

 even inaccurate) use of terms, besides the frequency in biological 

 terminology of the use of the same word in several meanings, and 



1 Heim, Mechanismus der Gebirgebildung, Basel, 1878. 



a Lehmann, Entstehung der Altkrystalischen Schiefergesteine % B.jnn., 18S4 



