July 31, 1879] 



NATURE 



m 



right in saying that "the theory of no farm plant has 

 been worked out," and that "our turnip shows are con- 

 ducted on no useful principle." But he is not equally 

 correct in affirming that " the chemist of the Aberdeen- 

 shire Agricultural Association initiated a most important 

 mode of teaching one aspect of cultivation," or that ques- 

 tions in agricultural botany "have usually been altogether 

 subordinated to questions on the comparatire efficacy of 

 manures. Had Mr. Wilson known the range of work 

 and style of teaching until lately prevailing at Cirencester, 

 and for long and now in vogue in many agricultural col- 

 leges in America and on the Continent, he would have 

 hesitated before making such statements. 



While Mr. Wilson shows us how, under certain condi- 

 tions, a larger weight per acre of roots was produced 

 when the plants (both turnips and swedes) were singled so 

 as to leave but 6 inches between them in the drills, although 

 the drills themselves were 27 inches apart, he gives us no 

 information as to the relative feeding values of the larger 

 roots grown at 8 and 9-inch intervals, and the smaller but 

 more numerous roots from the 6-inch intervals. Had 

 the average weight of any of these sets of roots been 

 exceptionally high or exceptionally low, this point would 

 have been of much greater importance. For our object 

 in growing such a crop as turnips or swedes is to obtain the 

 most economical production of the greatest amount of 

 wholesome and keeping food per acre. Very large roots 

 are, we know, very watery, do not keep well, and contain 

 certain nitrogenous and saline matters in excess, so as to 

 become in this way also less desirable as food for farm 

 stock. And it frequently happens that all the increase 

 per acre obtained in the form of large roots is water or 

 useless mineral matters. Thus, in all experiments, such 

 as these of Mr. Wilson, fair samples of the crop from 

 diiferent plots should be reserved for analysis — water, ash, 

 and albuminoid nitrogen, at all events, being determined 

 in the produce of each plot. 



Arithmetic in TJieory and Practice for Higher and Middle 

 Class Schools, Sr'c. By Henry Evers, LL.D. (London 

 and Glasgow: W. Collins, Sons, and Co., 1878.) 

 Had Dr. Evers been entirely unknown to us, we should 

 have had no hesitation whatever in saying that this is the 

 work of a practical teacher ; of one who has fully realised 

 the difficulties of " teaching arithmetic," and by long ex- 

 perience and patient observation learnt to cope with those 

 difficulties successfully. The arrangement is unquestion- 

 ably good and in some respects original ; the definitions 

 and explanations are short and to the point, indeed we 

 could wish in some cases the author had made them 

 fuller; the problems are numerous and interesting and 

 more of the ordinary daily business type than fanciful 

 improbabilities ; and the solutions as far as we have 

 examined them remarkable for accuracy. 



The author might have given another method for the 

 extraction of the cube root applicable to all roots ; those 

 he gives are certainly the best we remember seeing in any 

 text-book. The examination questions at the end will be 

 found of very great value to those preparing for similar 

 ordeals. The publishers have as usual given a good book 

 a good dress as regards paper, type, and binding. 



E. H. 



LETTERS TO THE EDITOR 

 [ 7'ht Editor does not hold h imself responsible for opiniotis expressed 

 by his correspondenls. Neither can he undertake to return, or 

 to correspond with the writers of, rejected manuscripts. No 

 notice is taken of anonymous comtnunications . 

 [ The Editor urgently requests correspondents to keep their letters as 

 short as possible. 1 he pressure on his space is so great that it 

 is impossible othcnuise to ensure the appearance even of com- 

 munications containing interesting and novel f(uts.\ 

 The Recent Weather 

 It is not necessary to appeal to statistics to demonstrate the 

 cold and sunless character of the weather nearly constantly 



experienced during the last few months, this being matter of the 

 most ordinary observation ; nevertheless some more exact infor- 

 mation on the subject may not at the present time be unaccept- 

 able to the readers of Nature. 



The year 1878 until October had been generally warm, the 

 temperature on the whole having been above the average in 

 every month, excepting September, and it was very little below 

 in this month. Then a period of cold set in. Beginning with 

 1878, November, the temperature has been in every month 

 below the average, the deviation in some months being very 

 large. The amount of sunshine, as recorded by Campbell's 

 instrument, has also, since April, been in each month remarkably 

 small. A few particulars, extracted from the Royal Observatory 

 Records, by permission of the Astronomer-Royal, are given in 

 the following table : — 



The sign - indicates below the average. 



In every month the temperature has been below the average. 

 The generally severe character of all the months, excepting 

 February and March, is well shown in the column giving the 

 number of days on which the temperature was below the average. 

 From April i to July 19, a period of no days, 97 were below 

 the average. And during the same period the hours of bright 

 sunshine numbered only 405 -o, which is 192-4 hours less than 

 the average of the same period in the two preceding years, or 

 0-68 only of the amount registered in those years. 



Royal Observatory, Greenwich, July 23 William Ellis 



Some Remarks on the Rev. J. G. Wood's Explanatory 

 Index to " Waterton's Wanderings " 



1. The name of the Indian tribe mentioned ought to be 

 Tamanacos and x\aijamunacs. 



2. The b0tanic.1l name of the arrow-reed is Gynerium (not 

 Gyncecium, p. 372). 



3. (P. 378). — The Ealata gum has reached the English market 

 long ago, though it may have disappeared again. If I do not- 

 mistake there existed about 1864 even a Batata Gum Company, 

 in which Messrs. Silver and Co. took the lead. We have in 

 Venezuela (State of Maturin) the same tree, where it is called 

 Purvio. Mr. d'Azevedo, of Maturin, sent Feveral times quanti- 

 ties of the gum to Hamburg, but I am informed it did not pay, 



4. (P. 380). — The Camoudi\i,Eunectesmurinus(r,o\.'a\axvciXi'i). 

 Mr. William Crookes in his article " Gravitation as a Factor in 

 the Organic World" (yournal of Science, January, 1879, p. 42), 

 calls it aquatic, and tays that it inhabits the rivers of South 

 America. This is certainly wrong ; it is generally found near 

 the water, and swims very well, but is by no means an aquatic 

 animal. 



5. (P. 381). — Copaiva is an oleo-resin, and should not be called 

 a gum. There is on p. 461 a misprint in the name of the tree 

 from which it is obtained. It is Copaifera pubiflora, Benth., not 

 C. publiflora. 



6. (P. 383).— The name of the describer of the bird? of 

 Trinidad is Z('(;/rtH</ ("Oiseaux de I'lle de la. Trinidad," Port 

 d'Espagne, 1866). 



7. (P. 384).— The castor-oil plant belongs to the family of 

 Euphorbiacesc, but not to the tribe of Euphorbia: (or better 

 EuphorbicDc). 



8. (P. 385). — Read Anolis instead of Anolius. 



9. (P. 394). — The coffee-tree does not belong to the "useful 



