May 13, 1880] 



NATURE 



29 



usefully employ their leisure, by contributing to geological 

 literature, and we heartily wish him success in his work. 



Ensayo sobrt una nucva enfet incdad del Olivo. For Don 

 Pablo Colv^e. Publicado en la Gaceta Agricola del 

 Ministerio de Fomento. Pp. 43, pi. i-ii. (Madrid, 

 1880.) 

 It appears that the Spanish olive crop is being jeopardised 

 in the neighbourhood of Valencia by an insect of the family 

 Coccidu-, distinct from Lccanium olccc, already known as 

 attacking the olive, and considered by Don Pablo Colv^e 

 to be a new species of the genus Aspidiolus, which he 

 describes as A. oka. It apparently attacks the tree 

 generally, but especially the fruit, causing the full develop- 

 ment of the latter to be arrested. The greater part of 

 Don Colvee's paper is occupied by considerations on the 

 development of insects in general, and on those attacking 

 the olive in particular. The author appears to suggest no 

 special remedy, but judiciously invites investigations as 

 to whether the attacks of the insect are the primary 

 cause of the want of health in the trees, or whether the 

 latter does not invite the attacks. 



LETTERS TO THE EDITOR 



\The Editor does not hold himself responsible Jor opinions expressed 

 by his corresf'ondatts. A^cither can he undertake to rettirn, or 

 to correspo7id with the writers of, rejected mamiscripts. No 

 notice is taken of anony??ioiis 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- 

 municatiotis containing interesting and novel facts.'] 



Winter "Swallovirs" 



Some months ago I tried to investigate, so far as possible, the 

 many recorded occun-ences of swallows in this country in winter. 

 As miijht be expected, a large proportion of them broke 

 down on inquiry, but there was one which, for several reasons, 

 I thought might be safely trusted. It appeared in the " Remark^; 

 on the Weather during the Quarter ending 31st of March, 1864 " 

 (p. 5), appended to the Registrar-General's Report for that 

 period, and stands thus : — 



"Swallows were seen on January 22d, three miles south of 

 Granth.im." 



Through the kindness of Mr. Glaisher, F.R.S., and of Mr. 

 Jeans of Grantham, I was at last put into communication with 

 the original circulator of the statement, who obligingly wrote to 

 me (omitting names) as follows : — 



" Grantham, Sept. 23d, 1S79 



"Sir, — The information given to respecting the 



swallow.":, I discovered some time afterwards was not correct ; 

 what was taken to be swallows were the common bat. I much 

 regret being instrumental in incorrect statements being published ; 

 it was an Irishman in my employ who told me of them ; he some 

 time afterw.irds showed me what he supposed to be swallows. 

 "I remain, sir, 



" Your obedient servant, 



I leave to others the moral th.at may he drawn from the above. 



Alfred Newton 

 Magdalene College, Cambridge, May 9 



Does Chlorophyll Decompose Carbonic Acid? 



I HAVE read with much interest in NATURE, voh xxi. p. 557, 

 Prof. Lankester's remarks on the question — Does Chlorophyll 

 decompose Carbonic Acid? and having many years ago made 

 experiments on that and kindred topics, should be much obliged 

 if you will do me the favour to reprint the following extract from 

 a paper I published in the Philosophical ATagazine (December, 

 1872, p. 425, &c.). This is also in my scientific memoirs, 

 p. 409, 410. 



"The decomposition of carbonic acid by plants is undoubtedly 

 the most important of all actino-chemical facts. The existence 

 of the vegetable world, and, indeed, it may be said, the existence 



of all living things, depends upon it. I first effected this decom- 

 position on the solar spectrum, as may be found in a memoir in 

 the Philosophical Magazine (September, 1S43). The results 

 ascertained by me at that time from the direct spectrum experi- 

 ment, that the decomposition of carbonic acid is effected by the 

 less, not by the more refrangible rays, have been confirmed by 

 all recent experimenters, who differ only as regards the exact 

 position of the maximum. In the discussions that have arisen, 

 this decomposition has often been incorrectly referred to the green 

 parts of plants. Plants which have been caused to germinate 

 and grow to a certain stage in darkness are etiolated, yet these, 

 when brought into the sunlight, decompose carbonic acid, and 

 then turn green. The chlorophyll thus produced is the effect of 

 the decomposition, not its cause. Facts derived from the vi-ible 

 absorptive action of chlorophyll do not necessarily apply to the 

 decomposition of carbonic acid. The curve of the production 

 of chlorophyll, the curve of the destruction of chlorophyll, the 

 curve of the visible absorption of chlorophyll, and the curve of 

 the decomposition of carbonic acid are not all necessarily 

 coincident. To confound them together, as is too frequently 

 done, is to be led to incoiTect conclusions." 



Nothing can act before it exists, nothing can originate itself. 

 Chlorophyll is therefore the result, not the cause, of the decom- 

 position. Its continual inci-ease during the life of a plant is an 

 effect of the same kind. The force decomposing carbonic acid 

 does not reside in chlorophyll, but elsewhere in the structure of 

 the leaf. JOHN William Draper 



University, New York, April 2S 



On a Point Relating to Brain Dynamics 



Any attempt to grapple with the doctrine of Free Will v. 

 Necessity on the old lines would probably (and deservedly so) 

 not attract much attention. The object of this paper is to place 

 a consideration of extreme simplicity under critical notice, which 

 would seem to be capable of affording a key to the complete 

 reconciliation of the divergent views on a common basis ; and 

 since the matter to be dealt with will be strictly within the domain 

 of natural science, a clear analysis will be rendered possible. 



It is well known that the only attempt to harmonise the 

 doctrine of Free Will with the principle of the Conservation of 

 Energy consists in supposing that living creatures have a power, 

 by the mere exercise of their " will," of deflecting particles of 

 matter within their bodies from their natural paths, without 

 thereby altering the total energy of the particles.^ This, there- 

 fore, it will be observed in the first instance, assumes a peculiar 

 physical state of things to exist within the body of an animal 

 which does not prevail elsewhere, or it supposes that the laws of 

 nature have not a general application, but that the animal world 

 must be made an exception. This at the very outset evidently 

 involves a very questionable admission. My purpose is simply 

 to point out that by taking into account a special consideration 

 ba-ed on the evidence of modern physiology as to the functions 

 of the brain, such an assumption as the above is rendered 

 entirely superfluous, and that even if it could be supported it 

 would still miss the main object in view. 



Whatever room for speculation there may be as to the exact 

 nature of the mental facidties, it is at least very generally 

 admitted that these faculties are most intimately connected with 

 or dependent on brain structure. Modern physiological research 

 has at least placed this fact beyond question, or it is allowed 

 that the mental faculties have at all events a physical side. From 

 this it must follow therefore that what we call " identity," 

 character, or individuality (as involved in "mind") must be 

 dependent on the special structure of the brain ; indeed this view 

 is so widely prevalent that it becomes almost superfluous to 

 insist upon it. Now it may be safely assumed that no upholder 

 of Free Will would wish for more than that a person should act 

 in strict accordance with his identity or individuality, for the 

 object of Free Will certainly is not to annihilate individuality 

 (or those personal trails which constitute character). But is not 

 this precisely what would cccur if this contention for a myste- 

 rious power of deflecting particles within the body could be 

 carried out ? for the efi'ect of this contention would be to make 

 the brain superfluous as a directing mechanism, which would be 

 tantamount to abolishing it (together with the individuality, of 



I The necessity for this special assumptlcn. in order to prevent Free Will 

 from coming into direct collision with the principle of the Conservation of 

 Energy, is so obvious that it will probably be regarded as superfluous to 

 give references to particular authors. 



