124 



NATURE 



[Dec. 12, 1889 



price of timber and the high rent at present obtained by 

 the letting of grouse moors and deer forests. 



Upon data which cannot be gainsaid, Dr. Schlich has 

 based important calculations, which will be found on 

 pp. 17-19. Space forbids the discussion of details, but 

 the result is that Scotch pine forests cannot be expected 

 to yield more than 2^ per cent, on the capital invested 

 (the value of the land and of the growing crop). 



"All land, therefore, which can be let for the raising of 

 field crops, for shooting, or other purposes, at a rental 

 equal to, or upwards of, 2^ per cent, of the capital value of 

 the land, had better be so let. On the other hand, land 

 which would realize a rental of less than 2h per cent, of 

 its value, may with advantage be planted with Scotch 

 pine or other similarly remunerative trees." 



These conclusions are based upon circumstances as 

 they exist at the present time. But a change of circum- 

 stances is not impossible. The author points out that 

 6,000,000 loads of timber are imported annually into the 

 United Kingdom from Europe and North America, and 

 that only a small portion of the forests which furnish this 

 large supply are under systematic management and con- 

 trol. It may be regarded as certain that the supply from 

 Sweden and Norway and from North America, amounting 

 at present to nearly 4,000,000 loads a year, will continue 

 to diminish, and, under the circumstances of the case, the 

 necessary result of such diminution will eventually be a 

 rise in the price of timber. Again, if proprietors of wood- 

 lands in England and Scotland were in a position to offer 

 large quantities of home-grown timber of good quality for 

 sale, regularly at stated seasons, timber traders would 

 make their arrangements accordingly, and in many cases 

 better prices would be obtained. Firewood is at present 

 almost unsaleable in the United Kingdom, but if— and 

 this may happen — the price of coal should rise consider- 

 ably, firewood would in some districts become an article 

 of general consumption, as it was 150 years ago, and 

 to some extent this would improve the money yield of 

 woodlands. 



It is not too much to say that the publication of Dr. 

 Schlich's manual will give a powerful impetus to sys- 

 tematic forest management in the United Kingdom, in 

 India, and in the vast colonies of the British Empire — in 

 fact, wherever the English language is spoken. 



D. Brandis. 



FERREL'S THEORY OF THE WINDS. 



A Popular Treatise on the Winds. Comprising the 

 General Motions of the Atmosphere, Monsoons, 

 Cyclones, Tornadoes, Waterspouts, Hailstorms, &c. 

 By William Ferrel, M.A., Ph.D., &c. (New York: 

 John Wiley and Sons. London : Macmillan and Co. 

 1889.) 



^]UMEROUS as are the popular treatises on various 

 *! branches of phenomenal meteorology that have 

 appeared during the last quarter of a century, English 

 literature has hitherto been singularly deficient in ele- 

 mentary works treating of the physical and mechanical 

 processes of the atmosphere from a theoretical point of 

 view, and suited to the capacity of the average student. 

 Those versed in the higher mathematics may indeed find 



all they require in such modern works as Sprung's 

 " Lehrbuch der Meteorologie," and Ferrel's " Recent 

 Advances in Meteorology," the high merit and originality 

 of which last are somewhat veiled under its more obtru- 

 sive title — " Part 2 of the Report of the Chief Signal 

 Officer of the [U.S.] Army for 1885." But these works are 

 hardly suited for popular instruction ; and for that large 

 class of students whose mathematical acquirements are 

 more limited, but who nevertheless desire to understand 

 the movements and internal changes of the atmosphere, 

 and to interpret them rationally in accordance with me- 

 chanical and physical laws, there has hitherto been little 

 guidance, save such as they may obtain from casual 

 references to them in works devoted to the general 

 teaching of these sciences. It is perhaps in consequence 

 of this divorce of the deductive from the inductive treat- 

 ment of meteorological subjects that the contributions of 

 English observers to the science of meteorology bear 

 but an insignificant proportion to the labour expended on 

 observational work, and that so much of this work is 

 abortive, and practically of little value, owing to the 

 absence of guiding and suggestive theoretical knowledge. 



It is, then, with no ordinary degree of satisfaction that 

 we hail the publication of Prof. Ferrel's treatise, the title 

 of which heads this notice. As the originator and dis- 

 coverer of many of the most important problems dealt 

 with in these pages, no one could be better fitted to 

 explain them in terms suited to general comprehension, 

 and this task he has performed with a completeness and 

 lucidity which leave but little to be desired. The work 

 is, as it professes to be, a " popular " treatise, but popular 

 only in the higher sense of the word. A system of move- 

 ments so complex as those of the earth's atmosphere 

 cannot be made clear to anyone who is not capable of 

 following a chain of close reasoning, or who is not pre- 

 pared to bring to the study that concentrated attention 

 that is requisite to master any problem in deductive 

 science. But, these being granted, no further demand is 

 made on the student than some familiarity with the 

 elements of algebra, and the simplest conceptions of 

 plane trigonometry and kinetics. The action of the 

 mechanical and physical forces that determine and 

 regulate the wind system of the globe is clearly ex- 

 plained in the first two chapters of the work. 



The most important and original portion of the book 

 is that which deals with the general circulation of the 

 atmosphere, in relation to which the cyclones and anti- 

 cyclones that cause the vicissitudes of local weather are 

 but matters of subordinate detail. The magnitude of the 

 work achieved by Prof. Ferrel in this field has hitherto 

 been recognized only by the few. It is not too much to 

 say that he has done for the theory of atmospheric circu- 

 lation that which Young and Fresnel did for the theory of 

 light ; and that the influence of his work is not more 

 generally reflected in the literature of the day, must be 

 attributed to the want of some popular exposition of the 

 theory. 



Starting with the fundamental conditions of a great 

 temperature difference between equatorial and polar 

 regions and a rotating globe, and postulating in the first 

 instance a uniform land or water surface, it is shown 

 how the convective interchange of air set up by the 

 former must result in producing two zones of maximum 



