April 15, 1880] 



NATURE 



56i 



to the entomologist, but also to the practical cultivator, 

 whether of field or garden crops. The persistent energy 

 with which Miss Ormerod and her coadjutors have ad- 

 vanced these inquiries, the result of which is the full and 

 elaborate report before us, is worthy of all praise. It is 

 satisfactory to learn that for the coming year a large 

 number of fresh observers have promised their help, and 

 with the hope that this notice may induce some of our 

 readers to communicate their own experiences to Miss 

 Ormerod at Dunster Lodge, Spring Grove, Isleworth, we 

 may perhaps mention the following as a guide to the kind 

 of information required : — 



1. Any notes as to the extent of insect injury, and esti- 

 mated pecuniary loss from such. 



2. Remedies found of practical use in checking such 

 ravages. 



3. Any notes of coincident circumstances such as of 

 weather influences, or surroundings, or state of the soil 

 which may increase or diminish insect attack. 



It is pointed out that even the shortest notes are valu- 

 able when collated with others, and the importance of 

 noting down the observations as they occur is also 

 impressed upon observers. 



John R. Jackson 



LETTERS TO THE EDITOR 

 [The Editor does not hold himself responsible for opinions expressed 

 by his correspondents. Neither eon he undertake to return, or 

 to correspond with the writers of , rejected manuscripts. Xc 

 notice is taken of anonymous communications. 

 [ The Editor urgently requests correspondents to keep their letters as 

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

 is impossible otherwise to ensure the appearance even of com- 

 munications containing interesting and novel facts. ] 



The Density of Chlorine 

 Ix Nature, vol. xxi. p. 350, my friend, Mr. F. D. Brown, 

 5 that the low density of chlorine at high temperatures may 

 be explained on the assumption that it undergoes decomposition 

 in the sense of the equation CL = 2CI, thereby renewing a 

 suggestion made by Lieben in a communication to the French 

 .my shortly after the publication of V. and C. Meyer's 

 paper. 

 A few days ago it might have been said that, however probable 

 such an explanation might appear to be on general grounds, there 

 « as ii thing in the Meyers' observations to justify it rather than 

 the alternative hypothesis that the chlorine underwent decom- 

 position into other as yet unkniwn substances. On the contrary, 

 taking into account Meyer's observations on iodine, which by 

 reason of their greater number may be regarded as furnishing 

 mere conclusive testimony than the more limited series with 

 chlorine, there was apparently distinct evidence in favour of the 

 latter view. The dissociation of iocHne, according to Meyer, 

 takes place within a range of about 400° C, between 603° and 

 I,O00°, and a further increase of nearly 600° is practically without 



hcreas had the change been of the character indicated 

 by Mr. Brown, a further diminution in density ought to have 

 been observed, 



.t communication to the French Academy by Crafts 

 and Meier, however, materially advances the discussion. Thee 

 observers maintain that Meyer's estimates of temperature (made 

 by the calorimetric method with a platinum block) are excessive, 

 and that, in fact, the highest temperature realisable with the 

 Perrot gas-furnace (determined by an air thermometnc method), 

 is 1,390° instead of about 1,570°. They have also obtained a 

 considerably lower value for the density of iodine at the highest 

 temperature of the furnace, the quotient of the theoretical density 

 (I. = S786) by the observed density being -6o for their highest 

 observation, and '65 for Meyer's. Their results are as fol- 

 lows : — 



Temperature. 



445 



S30-SS0 



1,020-1,050 



1.275 



I.390 



Density. 



870 878 875 



8-04 8" 1 1 



702 7-18 6-83 



6-07 5-57 



S'23 S'33 



Should it ultimately be proved that the molecules of the halogens 

 are thus dissociable, our present views regarding phenomena such 

 as the nascent state and the influence of light in inducing hydrogen 

 and chlorine to enter into reaction will meet with much support 

 the appeal as to their elementary nature will then be entirely 

 thrown on the spectroscope for decision. 

 London Institution, April 10 Hexry G. Armstrong 



The Omori Shell Mounds 



I HAVE received the enclosed letter from Frof. Morse, with a 

 reque-t that I should forward it to you. I hope that it may be 

 published, for the article in Nature to which it refers seemed 

 to me to do very scant justice to Trof. Morse's work. I refer 

 more especially to the evidence adduced by him on cannibalism 

 by the ancient inhabitants of Japan — on their platycnemic tibia; 

 — on their degree of skill in ceramic art — and beyond all other 

 points, on the changes in the molluscan fauna of the islands 

 since the period in question. 



It is a remarkable fact, which incidentally appears in Pr r. 

 emoir, that several Japanese gentlemen have already 

 firmed large collections of the shells of the Archipelago, and 

 have zealously aided him in the investigation of the prehistoric 

 mounds. This is a most encouraging omen of the future progress 

 of science in Japan. Charles Darwin 



Down, Beckenham, Kent, April 9 



In Nature, vol. xxi. p. 350, is a review of my memoir on 

 "The Omori Shell Mounds" by Fredk. V. Pickins. I do not 

 now heed the spirit in which it is written, nor would I deem it 

 worthy of notice did it not occur in the pages of your widely- 

 read magazine. One expects in a reviewer some knowledge of 

 the subject he reviews. Mr. Dickins, by a series of mistakes, 

 bethtys his ignorance of the whole matter. The extraordinary 

 blunder he makes regarding the Ainos has already been promptly 

 corrected by a Japanese gentleman residing in London. It is 

 charitable to assume that Mr. Dickins has lived in Japan, other- 

 wise he would not, in common with so many of his countrymen, 

 commit the wilful blunder of calling the principal city of the 

 empire by its wrong name. On the other hand, it is impossible 

 he could have seen the Omori deposits, otherwise he would not 

 make another blunder by expressing his be'ief that they have 

 been completely swept away, when in truth but a small portion 

 of them have been removed. He says : " These mounds c 

 for the most part of shells, little, if at all, distinguishable from 

 what are still found in abundance along the shores of the Gulf 

 of Y.'do." Had he taken the trouble to read the memoir he 

 attempted to review- he would have seen that all the species 

 occurring in the mounds vary in size, proportion of parts, and 

 relative abundance of individuals from similar species living 

 the shores today. That some species extremely abundant 

 in the mounds are scarcely met within the vicinity, while one 

 species has never been found within 400 miles of Omori ; indeed, 

 it belongs to a different zoological province ! 



Ilis complaint at the large number of plates given to the 

 illustration of pottery, tablets, & L \, shows how incapable he is 

 of appreciating that part of the work which has received the 

 highest commendation from archaeologists, namely, the pre- 

 senting as far a^ possible an exhaustive illustration of every form 

 of vessel and variety of ornamentation. He laments the absence 

 of a plate giving figures of the bones and shells, especially the 

 latter, that are stated to belong to extinct species. Had he I: 

 at the last plate (a copper plate, by the way, and not a litho- 

 graphic one, as he calls it) he would have seen every species, 

 with one exception, figured, when similar forms from the 

 11 ring shores could be got for comparison. 

 I did not feel justified in comparing shell-mound forms with 

 similar forms from Niigata, Kobe, or Nagasaki, and the rs 

 w ill be obvious to any one having the -lightest familiarity with 

 the variations that species show in widely separated localities. 



