830 Mr. B. W. Davy on a New Test for 



less transitional. The typical populations of the centre spread 

 them at the expense of the sub-typicals of the periphery until 

 the extremes meet. 



3. The circumpolar populations supply similar illustrations. 

 Beginning with Scandinavia, the Lap stands in remarkable con- 

 trast with the Norw^egian of Norway, and the Swede of Sweden. 

 Why is this ? Because the Northman represents a population 

 originally German, — a population which, however much it may 

 have graduated into the type of the most southern congeners of 

 the Lap, is now brought into contact with a very diflferent mem- 

 ber of that stock. 



4. This phsenomenon repeats itself in the arctic portions of 

 America, where the Algonkin and Loucheux Indians (Indians of 

 the true American type) come in geographical contact, and in 

 physiological contrast, with the Eskimo. Consequently along 

 the Loucheux and Algonkin frontiers the line of demarcation 

 between the Eskimo and the Red Indian (currently so-called) is 

 abrupt and trenchant. Elsewhere, as along the coast of the 

 Pacific, the two classes of population graduate into each other. 



5. The African family is eminently isolated. It is, however, 

 just along the point of contact between Africa and Asia that the 

 displacements have been at a maximum. The three vast families 

 of the Berbers, the Arabs and the Persians, cannot but have 

 obliterated something (perhaps much) in the way of transition. 



6. The Bushmen and Hottentots are other instances of ex- 

 treme contrast, t. e. when compared with the Amakosah Caffres. 

 Yet the contrast is only at its height in those parts where the 

 proof of CafFre encroachment is clearest. In the parts east of 

 Wallfisch Bay — traversed by Mr. Galton — the lines of differ- 

 ence are much less striking. 



Such are some of the instances that illustrate what may be 

 called the " subjectivity of ethnological groups,"— a term which 

 greatly helps to reconcile two apparently conflicting habits, viz. 

 that of thinking with the advocates of the unity of the human 

 species, and employing the nomenclature of their opponents. 



LIII. On a New Test for Nitric Acid and the Nitrates. By 

 Edmund William Davy, A.B., M.B., T.C.D., Lecturer on 

 Chemistry in the Carmichael School of Medicine, 5fc., Dublin^. 



THE want of a simple and satisfactory test for minute quan- 

 tities of nitric acid and its salts has long been felt by those 

 engaged in chemical research ; for though a number of methods, 

 more or less delicate, have from time to time been proposed, 



* Communicated by the Author. 



