HARDWICKE'S SCI ENCE-GOSSIF. 



24.9 



may conclude that the sample has been either 

 adulterated with foreign leaves (which can easily be 

 recognised by their botanical structures under the 

 microscope, as I have alluded to at the commence- 

 ment of this article), or the leaves have been 

 ■exhausted. 



The author has experimented upon various teas, 

 among which may be mentioned, "Souchong," 

 ■"Orange-Pekoe," and "Paraguay Tea" {Ilex 

 Taragitaye^isis). The smallest percentage of theine 

 was yielded by a sample of Paraguay tea. 



This Ilex Paraguayertsis is a kind of holly of South 

 America ; and the beverage it yields with water is 

 called Mate by the natives. 



Besides the crj'stallisable alkaloid theine or caffeine 

 (CgHioN^Oo) which belongs to the family of " organic 

 "Compound containing triad and pentad nitrogen ; " 

 ■the principal ingredients are an essential oil and 

 tannin. The exhilarating effect of tea (which 

 induces such a large proportion of the human race 

 to partake of it in their daily diet) is owing to the 



Fig. 147.. 



■Thea viridis [b shows flowers on a larger 

 scale man a). 



presence of the above three constituents. The essential 

 oil is the ingredient that gives an infusion of tea 

 the aromatic flavour ; theine combined with the 

 essential oil stimulates the stomach, and by inducing 

 a slight perspiration, gives a lightness and increased 

 strength to the body of the consumer. 



The astringency of tea is due to the tannin present. 



The base theine (in ordinary tea) is combined with 

 tannic acid, forming tannate of theine. The author 

 comes to th2 conclusion that in the process of 

 extraction just described, the mixture of glass and 

 magnesic oxide has the power of liberating tannic 

 acid, which may combine with a portion of the 

 magnesic oxide, forming magnesic tannate, or the 

 tannin may be left in an uncombined state, but being 

 almost insoluble in ethylic ether, is by this means 

 separated from the base theine. 



There are three varieties of T/iea Chmensis, 

 namely, Thea viridis, Thca Bohca, and Thea 

 Assaniica ; all of them yielding green and black tea. 



The difference in colour and quality of teas depends 

 chiefly on the time of the year when gathered, and 

 also the method employed in drying the leaves ; — and 

 for this reason, also, the variation in the percentage 

 of theine (that is between a half and five per cent.). 



A GOSSIP ABOUT NEW BOOKS. 



A FEW months of unusually hard work in other 

 directions have compelled us to defer the 

 notice of various new books of importance until the 

 commencement of the "reading season," It is not 

 too late, however, to draw the attention of our 

 readers to them now, and our high opinion of 

 Anthropology: an Introduction to the study of Man 

 and Civilisation, by Dr. E. B. Tylor (London : 

 Macmillan & Co.), is best indicated by our selecting 

 it as the first on which to make a few remarks. 

 It is always a treat to read a book written by the man 

 who best knows his subject, and this is the case with 

 that before us. The subject is treated from the 

 evolution standpoint, but so calmly and dispassion- 

 ately, and without the slightest offence even in the 

 most sensitive regions, that the author proves himself 

 a philosopher by his tact alone. We have read the 

 book through with much pleasure — a task rendered 

 all the more delightful by the plain but attractive style 

 in which it is written — and we cordially recommend 

 it to the student as by far the best and clearest and 

 fullest manual of Anthropology in the English 

 language. Its cheap price places it within the reach 

 of almost the poorest reader. 



Studies in the Theory of Descent, by Dr, Aug. 

 Weismann, Part II. (London : Sampson Low & Co.), 

 deals in the present part with "The Origin of the 

 Markings of Caterpillars," and " Phyletic Parallelism 

 in Metamorphic species." Mr, R. Meldola (vice- 

 president of the Entomological Society of London) 

 has ably translated and edited the work, and enriched 

 the author's remarks and comments by additional ones 

 of his own. This work casts new light on the study 

 of Entomology. It is not many years since this 

 branch of natural science was regarded as inimical 

 rather than helpful to the doctrine of Evolution, and 

 now we find it acting as one of the richest contribu- 

 taries to that theory. Or rather, the theory helps us 

 to understand what before was either completely 

 overlooked, or regarded as hardly worth the trouble 

 of investigating. Here, for instance, is Dr. Weismann 

 devoting himself to the task of carefully observing the 

 various changes which the caterpillars of certain 

 moths undergo after their first extrusion from the egg. 

 He finds that the markings on their skins, after 

 repeated moultings, are always in a certain order of 

 arrangement, and he regards them as presenting a 

 picture, so to speak, of phyletic development (that is, 

 the changes through which the species has passed in 

 its development). Thus, a number of species of 



