Jan. 13, 1 881] 



NA 7 URE 



241 



Prof. Salvador! for the admirable way in which he has 

 commenced his laborious task, and to express our hope 

 that he may bring it to a successful conclusion. In Mr. 

 Gould's gi-eat work on the " Birds of New Guinea " we 

 have a series of magnificent illustrations of all the more 

 remarkable forms of Papuan ornithology. Such a work 

 as that of Prof. Salvadori's was much wanted in order to 

 perfect our knowledge of the history and literature of this 

 attractive subject. 



OUR BOOK SHELF 



An Elementary Treatise on the Integral Calculus, con- 

 taining Applications to Plane Curves and Surfaces; 

 with numerous Examples. By B. Williamson, F.R.S. 

 (London : Longmans, 1S80.) 

 Cf a //;/>;!? edition we need only remark that it is a carefully 

 revised issue of the second, and point out the few impor- 

 tant addhions that have been made. In the discussion 

 of Frullani's theorem (§ 119), a simple shape of the for- 

 mulas, due to Mr. E. B. Elliott, is given, and reference 

 made to other articles on multiple definite integrals by 

 the same gentleman (and by Mr. Leude^dorf) in the 

 Educational Times (1875) and in the Pi-oceedings of the 

 London Mathematical Society, 1876-7. A new article 

 (l itja) gives a proof of a simple character, by Zolotareff, of 

 the remainder in Lagrange's series. § 147 contains a re- 

 markable extension of Holditch's theorem, due to Mr. 

 Elliott {Mess, of Math. February, 1S78), and § 147^ 

 gives the " singularly elegant " theorem discussed by Mr. 

 Kempe {Mess, of i\fatli. ]'i\y, 1878), to which reference 

 is made in Prof. Minchin's letter in Nature (December 

 23, 1880), in which he proves these theorems from other 

 considerations. Various insertions of a minor character 

 increase the volume by more than twenty pages. A good 

 feature of the present edition is an index at the end of 

 the work. 



Bolanisches Centralblatt. Herau^gegeben von Dr. O. 

 Uhhvorm. Band i.. Quart. 1-4. (Cassel: Fischer, 1880.) 

 We are now able to record the completion of the first 

 volume of this valuable serial, a monument of extraor- 

 dinary energy on the part of the editor and his band of 

 assistants. The aim of the publication is to give an 

 abstract or resume of every import.-int contribution to 

 botanical science published in the scientific serials of the 

 Continent of Europe, Great Britain, and yVmerica ; and, 

 as far as we have been able to judge, the undertaking has 

 been carried out with great judgment and completeness. 

 Original works are also not neglected. Appearing much 

 more promptly than Jubt's " Jahrbuchcr," the " Central- 

 blatt " is indispensable to any one who desires to keep 

 abreast of any department of botanical science. 



Botany for Children ; an Illustrated Elementary Text- 

 i Booh for Junior Classes and Voung Children. By the 



Rev. George Henslow, M.A., F.L.S., &c. (London; 



Edward Stanford, 1880.) 

 We do not think that botany can be taught wi)h advan- 

 tage to children from books. No method of teaching 

 seems so well adapted to the wants of junior students as 

 that of demonstration. A flower pulled to pieces by the 

 student and the parts and their importance intelligently 

 explained by the teacher forms a lesson far more valua'ole 

 than any to be got from a text-book. With a few such 

 demonstrations from easily-obtained flowers, tal en as 

 they present themselves, most of the elementary facts 

 regarding flowering plants can be readily mastered, while 

 the habits of observation and the facility of dissecting 

 thus obtained are invaluable to the student. It is, we fear, 

 too much the habit in teaching botany to make the 



student prepare a lesson from the text-book as if it were 

 spelling or history. This is really what should be most 

 carefully avoided, although there must be a great tempta- 

 tion to proceed with the book lesson when the plant is 

 not obtainable. Mr. Henslow states in his preface ; "The 

 descriptions of flowers in this book are intended to form 

 botanical reading-lessons, specimens of the flowers being 

 at the same time placed in the hands of the pupils, who 

 are required to dissect and examine them carefully, and 

 be sure they see and understand each special part noticed 

 in the text." When used in accordance with the direc- 

 tions laid down by the author, the book seems an 

 excellent one , and calculated to serve its< purpose well, 

 although some very important types have been omitted 

 for want of space. As we have known children to work 

 out the structure of flowers for themselves by means of 

 this little book and to enjoy the exercise, we believe the 

 work will be deservedly popular. The illustrations are 

 rather coarse, but on the whole characteristic and often 

 give details of structure sometimes omitted from much 

 larger works. 



LETTERS TO THE EDITOR 



[The Editor does not hold himself responsible for opinions expressed 

 by his correspondt nts. Neither can he undertake to return, or 

 to correspond with the writers of, rejected manuscripts. No 

 notice is taken of anonymous communications. 

 The Editor urgently requests correspondents to hep their letters as 

 short as possible. The pressure on his space is so great that it 

 ts impossible otheriuise to ensure the appearance even of com- 

 munications containing interesting and novel facts.] 



Geological Climates 



I NOW procetd to justify my statement, wl ich has caused 

 Mr. Wallace great surprise, viz. : — 



" It is impossible to suggest any rearrangement of land and 

 water which shall sensibly raise the temperature <( the west of 

 Europe, or sensibly depress the temperature of the ea.stof North 

 America." 



It is proverbially difficult to prove a negative, and the only 

 way to do so in this case is to show that any given redisti ibution 

 of land and water is incapable of producing the effects ascribed 

 to it. 



I have already shown that Mr. Gardner's proposed redistribu- 

 tion by means of a land connection between Greenland and 

 Europe would fail to benefit the west of Europe. In like 

 manner I 'hall now demonstrate that Mr. Wallace's redistribution 

 of land and water is quite inadequate to raise the temperature of 

 the west of Europe. 



Mr. Wallace's proposal is to introduce two new Gulf Streams 

 into the Arctic Ocean, in addition to the present Gulf Stream. 



1. The fiiM of thee additional Gulf btreams would be the 

 Kuro-siwo, admitted through a widened Behring's Strait, the 

 effect of w hich, he estimates, would be to prcz'cnt altogether the 

 formation of /-v in the Aj'Ctie Sea. 



2. The second additional Gulf Stream is provided by allowing 

 the waters of tlie Bay of Bengal and of the Arabian Sea an 

 outlet to the north through the Caspian depre.'-sicin into the 

 Arctic Ocean. The effect of this second Gulf Stream, he esti- 

 mates, would he to raise the temperature of the Polar ocean from 

 1 5° A to 20° f. above the frecz'ng point of water. 



This mode of raisirg ihe lemperaiure of the Arctic regions, so 

 as to allow of the growth of their Miocene flora, occurred to me 

 when speculating on the former high temperatures of these lati- 

 tudes, but I rejected it as inadequate to account for the change 

 of climate required for the following reasons. But before giving 

 these reasons I w'sh to add that Mr. Wallace has given two 

 precie statements involving quantitative results, wiihout giving 

 the numerical gnunds on which he made those statements. 



The f llowing are the grounds on which I deny ihe adequacy 

 of Mr. Wallace's causes of ihange of climate : — 



[a) Air and Water. — Warm winds and cold winds ai e in 

 themselves of little consequence in influencing chmate, except 

 they blow over a Large expanse of warm or cold water ; they are 

 in fact only h«a! and cold carriers for the water. The specific 

 heat of water is more than four times that of air, and w ater is 815 

 times heavier, bulk for bulk ; therefore one cubic mile of water 

 will ccntain as much heat as 3260 cubic miles of air at the ; ame 



