Oct. lo, 1872] 



NA TURE 



473 



LETTERS TO THE EDITOR 



[ /'/;;' Editor docs not hoLl himself nsponsilih' for opinions expressed 

 by his correspondents. Mo notice is taken of anonymou:, 

 communications. ] 



Oceanic Circulation 



As some of your readers may be misled by Mr. Croll's reiterated 

 and uncontradicled assertion?, tliat he has demonstrated the 

 fallacy of the doctrine of Oceanic Circulation advocated by me, 

 I think it riyht tliat they should be made aware that these asser- 

 tions receive no support from the physicists and engineers, who 

 must be much better judges than either Mr. Croll or T can be, as 

 In the value of the (/<//.? on which his computations are based. 

 I lis arithmetic may be perfectly correct ; but if his fundamental 

 assumptions are wrong, or inapplicable to the case, his demon- 

 stration utterly fails. 



The report, now in the press, which I have presented to the 

 Royal .Society, as to the Deep-sea Researches, on which I was 

 occupied during the autumn of last year, contains my reply to 

 Mr. CroU's argument. And I profited by the unexpected delay 

 in its publication to bring the principal points of that reply before 

 the Mathematical and I'hysical Section of the British Association 

 :it its recent meeting, with the view of eliciting the opinion of the 

 authorities there assembled, as to the soundness of my argument. 



I do not think that I claim too much in saying that this opinion 

 was given by Sir AVilliam Thomson, and other distinguished 

 physicists, most explicitly in my favour. 



Having also had an opportunity of bringing the question under 

 the consideration of Mr. Ifawksley, whose experience as a 

 1-iydraulic engineer is probably second to that of no one living, 

 I found him entirely of my mind ; and Sir John Rennie has 

 repeatedly expressed himself as altogether concurring with me. 



So far as I know, therefore, Mr. Croll, in his reiterated asser- 

 tion that water will not find its own level — for that, in plain 

 Knglish, is the position he takes — stands "alone in his glory." 



Thcy;;c/j- which I embodied in a paper presented at the same 

 meeting to the Geological Section, in regard to the contrast of 

 temperature between inland seas and the ocean with wl'.ich they 

 communicate, seem to me inexplicable on any other view than 

 that of a deep nnderflo~,o of Polar water towards the Equatorial 

 area ; and this necessarily involve;, as its complement, an iifper 

 llo-.i' from the Equator towards the Poles. 



When Mr. Croll shall have given some other rationale of these 

 facts, he may fairly claim consideration for it. At present I 

 venture to submit that all \\\c facts :\\. j^resent known are in my 

 favour ; and that Mr. Croll's asserted refutation is purely theo- 

 retical. 



October 4 \Villi.\m B. Cakpenter 



Consciousness and Volition 



I.\ an interesting review of Lankester's "Comparative Lon- 

 gevity in Man and the Lower Animals," which recently appeared 

 in the 'J'iines, is the following sentence : — "Once commenced, its 

 continuance (that of the act of walking) is quite involuntary, and 

 may even be unnoticed Ijy the consciousness." I am anxious 

 to ascert.ain, from those readers of N.^ture who have paid 

 special attention to psychology, whether this is, in their opinion, 

 a correct statement of the condition of the mind during such an 

 habitual act as that of walking. There are undoubtedly certain 

 actions of the body, those denominated reflex, which are per- 

 formed without any exercise of the will whatever ; but these are 

 all either momentary, or, if continued, are nearly uniform and 

 unchanging. To me it seems impossible that any action which 

 is constantly varying can be wholly involuntary. Take, for in- 

 stance, the motion of the fingers in writing : we are absolutely 

 unconscious of the exercise of the mental faculties by which each 

 successive change in the position of the pen is regulated ; but yet 

 is it not certain that each up-stroke and down-stroke is the conse- 

 (pience of a separate effort of the will ? There is here an evident 

 connection between the state of mind at the time and the action 

 of the body ; and by wdiat other means is it possible to suppose 

 that the mental, act which conceives the word we are writing can 

 convey its instruction to the fingers ? Certainly not by any f>ro- 

 cess of instinct. A better instance perhaps is in the motion of 

 the muscles of the face and throat in speaking. These muscles 

 arc entirely under the control of the will ; and every separate 

 motion of them must surely be effected by a distinct voluntaiy 

 eflfort, of which however we are entirely unconscious. The same 



seems to me the case in walking. When we sway the body out 

 of the perpendicular in turning a corner, I am at a loss to 

 understand how this can be performed involuntarily. The ex- 

 planation seems to me to be that consciousness cannot, so lo 

 speak, work so fast as volition, and therefore cannot take cogni- 

 zance of a large number of rapidly successive acts of the will. 

 The question is not so much one of a nice metaphysical 

 distinction as simply of a correct use of terms, abhough I am 

 afraid I am opposing the viesvs of such high authorities as Hux- 

 ley and Carpenter. We have been made familiar with the term 

 Unconscious Cerebration. Is there not also an enormous field 

 of Unconscious Volition ? 



London, Sept. 28 AlI'RED W. Bennett 



Phosphorescence in Fish 



I II.WE noticed the phosphorescence in fish on two occasions. 

 Once on a calm night, wind light and sea smooth, in the S.E. 

 trades, lat. 18^ S., a shoal of porpoises was playing about under 

 the bows of the ship, and darting under her keel for a space of 

 nearly half an hour. Each looked like a piece of burnished 

 silver on blue velvet. They presented the most beautiful appear- 

 ance. We were not within "soundings." Every wavelet was 

 covered with phosphorescence during the whole of that night, 

 before and after the porpoises were seen. T/iey manifestly could 

 not have been the cause of this. As I leaned over the side and 

 watched them, it seemed to me that their phosphorescence re- 

 sulted from the condition of the w.ater. Off the coast of South 

 America, in about lat. 22" S. , long. 30° W., weather much the 

 same, a small shark accompanied the ship for some time, and 

 presented the same appearance. The sea was brilliantly phos- 

 phorescent. The fish could be seen deep down. In both cases 

 I saturated paper with the sea water. When dry the microscope 

 failed to detect any organic matter, nothing but crystals. 



II, Church Row, I-iampstead Arthur NicoLs ; 



On a Measuring Apparatus for Direct- Vision Spectro- 

 scopes 

 ."; There are few who possess Browning's "miniature," or other 

 small direct-vision spectroscojies, but must have felt the want of 

 some means of measuring the positions of spectral lines ; and, 

 indeed, little useful spectrum work is possible without it. I 

 think, therefore, a description of a simple arrangement I have 

 used for some time for this purpose may prove useful. 



In the " miniature " spectroscope the outer face of the prism is 

 inclined to the axis of the instrument at an angle of about 40°. 

 Opposite this a hole of about 2 mm. diameter is drilled in the 

 sliding tube, care being taken to avoid injury to the pi ism. It 

 is obvious that, through this aperture, lateral objects wdl be 

 visible superimposed on the spectrum. If now a scale be set up 

 opposite to the hole, it will be clearly seen, and t'ne lines may be 

 easily measured by it. The most convenient scale is one of 

 transparent lines on a dark ground (photographed on glass from 

 a scale drawn in black upon white paper), and illuminated by a 

 lamp behind. A paper scale, preferably drawn in white upon 

 black paper, may also be employed. In this case a common 

 retort-stand clamp serves conveniently to hold the spectioscope, 

 while the scale is laid horizontally on the table below. A sheet 

 of paper, may be substituted for the scale, and the instrument 

 used as a camera-lucida. Observation of faint spectra will be 

 much assisted by shading extraneous light with black velvet, and 

 covering the scale on paper with a black sliding screen, with an 

 aperture through which only one or two divisions of the scale can 

 be seen at once. A double scale, of which one gradation cor- 

 responds with the upper and the other with the lower edge of the 

 spectrum, is also advantageous. 



With a miniature spectroscope, and scale of millimetres at 

 25 cm. distance, the separation of Na and Li is about 13 divi- 

 sions, and can easily be read to o'2 mm. 



The arrangement would, I think, be very applicable to the 

 microspectroscope. The small hole is no inconvenience in ordi- 

 nary use, and can easily be covered by the finger or by a small 

 piece of black paper inserted in the tube. 



In conclusion, I would urge the necessity of noting a sufficient 

 number of reference lines at each observation, and the desira- 

 bility of reducing measurements to the wave-length scale, for 

 which purpose Dr. Watts' "Index of Spectra" will be found 

 invalu.able. 



North Shields Henry R. Procter 



