42 



NATURE 



\Nov. 20, 1873 



trary, I will mevely remark Ihat if you, or any of your numerous 

 readers who may feel interested in this subject, will favour me 

 with a visit to my establishment, I s'lall be happy to give the 

 fullest explanation as well as show the great difference existing 

 between the two, will point out the cause of failure in their 

 arrangement, and also the reason of the complete success of my 

 own thermometer. 



Though perhaps it is unfortunate for your correspondents that 

 their reference to Dr. Miller was not made during his lifetime, 

 yet, admitting that he said he was not aware of their arrange- 

 ment, I must ask in all seriousness. What had their thermometer 

 accomplished to make any one acquainted with it ? 



Facts speak for themselves. Their arrangement still remains 

 without result, whilst my thermometer, which has solved the 

 great problem of the true temperature of the sea even at its greatest 

 depths, has been adopted not only by our own Government, but 

 also by all the principal Governments and scientific authorities 

 throughout the world. Louis P. Casella 



147 Holboni Bars, Nov. 3 



Squalus spinosus 



On the 9th inst. tlie fishermen of Durgan, in Tlelford Harbour, 

 sent for me to look at a fish new to them, which had been caught 

 (with a \d. hook) on the preceding night near its entrance. 

 Congers had been numerous, but suddenly ceased to bite. The 

 fish (a spinous shark) had been hooked in the corner of its 

 mouth, out of the reach of its sharp teeth, had wound the line 

 many times round its body, which was 7 ft. in length, and 30 in. 

 in girth, being longer and more slender than one of which I sent 

 a notice to the Royal Cornwall Institution 3S years ago. The 

 back, sprinkled over with spines, was of a dark grey colour, the 

 belly nearly white. It was a male fish. The lobes of the liver 

 were 4 ft. in length. In the stomach was a partially digested 

 dogfish, 2 ft. long. The upper lobe of the tail was muscular 

 and long, perhaps to aid its ground feeding, the lower lobe 

 more marked than in Dr. A. Smith's drawing, as given by 

 Yarrel, and entirely unlike that of the Filey Bay specimen. 

 Twelve hours or more after its capture, when all e.xternal signs 

 of life had disappeared, I was surprised to observe the regular 

 pulsations of the heart. 



Prof. Hu.xley has not observed a correspondence between the 

 mass and large convolutions of the brain of a porpoise and its 

 intellectual power. 



Several years ago a herd of porpoises was scattered by a net, 

 which I had got made, to enclose some of them. It was strong 

 enough to catch tigers if set in the straits of Singapore, across 

 which they sometimes swim. The whole "senile" was much 

 alarmed, two were secured. I conclude that their companions 

 retained a vivid remembrance of the sea-fight, as these cetacea, 

 although frequent visitants in this harbour previously, and often 

 watched for, were not seen in it again for two years or more. 



Trebah, Falmouth, Oct. 27 C. Fo.\ 



Zodiacal Light 



It is a matter for regret that with the magnificent oppor- 

 tunities of investigating the character of the Zodiacal Light 

 afforded to Maxwell Hall by his elevated position in Jamaica, he 

 does not seem to have brought the powers of either the spectro- 

 scope or polariscope to bear on it, 



I think the full importance of the inquiry is hardly appreciated 

 by many. Taking tlie generally accepted theory of the light — 

 that of a lens-shaped disc of luminous matter, with the suu for 

 its centre and a diameter exceeding that of the earth's orbit — its 

 matter, lying as it does in the plane of the elliptic, actually con- 

 nects us with the sun, and may be the medium through which the 

 solar magnetic forces act upon our own. 



The intimate connection between solar outbursts, auroras, and 

 terrestrial magnetism is an established fact. 



To the aurora, the zodiacal light is by many conceived to be 

 nearly allied, and I do not think the evidence hitherto adduced 

 against this theory is at all conclusive. The remarkable wave of 

 light seen Ijy Maxwell Hall is strongly in favour of it ; and 

 though spectroscopic observations seem to point the other way, 

 they are as yet so scanty in number that it would be as unfair to 

 argue from them the want of connection between the two phe- 

 nomena, as it would be to assert that the planets have no volcanic 

 fires of their own because they only give us a reflected solar 

 spectrum. 



Assume the zodiacal light to consist of solid particles of mat- 

 ter — planet dust — shining by reflected light, and it is not difficult 

 to imagine the aurora playing amongst these tiny worlds, each of 

 which might have its own small magnetic system, swayed like our 

 own by the master magnet, the sun. 



So far as my own experience goes I can see no objections to 

 this assumption. Though I have seen the light very brilliant in 

 both its branches, I have never yet found it to have a decided 

 outline. Nor have I been able to trace it either east or west to 

 iSo° from the sun. Granting that this can be done, however, the 

 apparent vanishing point of the earth's shadow lies comparatively 

 near us, and far within this again is the point at which the shadow 

 would subtend only a degree or two of arc, and at which it would 

 be very hard to discern mid the feeble light of this portion of the 

 zodiacal light ; so that a slight extension of the diameter of the 

 disc would remove any objection that might be raised under this 

 head. 



Imagine one of Saturn's moons revolving in an orbit within 

 his belts, and fairly embedded in the matter, which, for the sake 

 of the argument, we must assume to be illuminated by the planet. 

 To inhabitants of that satellite each night would bring a pheno- 

 menon closely resembling our zodiacal light, only far more bril- 

 liant. At midnight two cones of light would taper upwards 

 east and west, and meet overhead. The brightest portion of each 

 cone would be that along the axis and nearest the horizon. To- 

 wards the summit and on the borders, where the line of sight 

 would lie through less depths of matter, the light would gra- 

 dually fade away, but from the satellite being embedded in the 

 belt, the entire sky would be more or less luminous. 



Has it not been noticed on our earth that when the zodiacal 

 light h.as been seen unusually bright, a " phosphorescence " of 

 the sky was everywhere visible ? May this not arise from our 

 solar belt in a somewhat similar manner? 



From my personal observations I see no reason to give a 

 lenticular form to the disc. Parallel faces would afford a per- 

 spective such as the zodiacal light appears to me. 



I would urge observers who may be fortunately situated, not to 

 neglect opportunities. .So far as I am able I shall do my best 

 to aid the work of inquiry, and with the powerful instruments 

 that Browning is forwarding me, placed at an elevation of more 

 than 6,000 ft., under the clear skies of our Indian winter, I trust 

 I shall be able to add something to our knowledge of the 

 zodiacal light. 



I should feel much indebted to any of your readers who 

 would inform me which is the best adapted polariscope for such 

 researches, and whose (amongst makers) speciality such instru- 

 ments are. E. li. Pringle 



Camp Udapi, .South Canara, Oct. 3 



Cold Treatment of Gases 



Allow me to submit to your readers the following sketch o 

 an apparatus for producing extreme cold, by which it might 

 perhaps be practicable to liquefy or even solidify the elementary 

 gases which have hitherto resisted the efforts of chemists. 



The gas to be operated on is compressed to any required 

 degree by means of one cylinder, is cooled to the lowest conve- 

 nient degree in the ordinary way, passes into an expansion 

 cylinder with a properly arranged cut-off, where in expansion its 

 temperature is still fnrtner lowered. From the expansion cylinder 

 it returns back to the compression cylinder, extracting the heat 

 from the counter current proceeding from the compression cylin- 

 der, so that the latter will be always arriving at the expansion 

 cylinder with a continually decreasing temperature. 



As out here I have no possible means of trying whether there 

 is anything in this idea, I offer it to any of your readers who 

 may feel disposed to try it. 



GraafT Reiuet College, Cape Colony, T. Gitturie 



July 19. 



'^The Relation of Man to the Ice-sheet 

 Mr. Tiddeman hjs shown for Yorkshire what I proved six 

 years ago for the South of England in a paper in the Geological 

 Mac;aziiic (vol. iv. p. 193), that glacial conditions have obtained 

 in this country since its occupation by Pala;ohthic man. Unfor- 

 tunately an attempt which I made to explain this coincidence 

 between his result and mine in a letter to the same periodical in 

 February last was rendered abortive by a clerical (or perhaps 

 printer's) error. I would press upon geologists to consider 



