KNOWLEDGE 



[Jan. 20, 1882. 



Assuming that by "jfut " ia Query 177 (p. 281) Mr. Webb means 

 the siphuDclr of the nautilus, the roost (ilausiblo explanation yet 

 given of its use iH tlmt by Mr. Senrles Wood — that, passing right 

 through all the clused iinil isolated chambers of the shell, it serves to 

 maintain the vitality of the entire organism during the animal's 

 certjiiuly long life. 



In answer to Query 18-1 (p. 231), Middleton's "Celestial Atlas" 

 is, or was, published by Jurrold & Son, of Korwich, and costs, with 

 the " Compauion," about ISs. Gall's is, I fancy, jniblishid by 

 Gall ii liigliii, who are Scottish publishers, I forget whether in 

 Edinburgh or Glasgow. The price of this 1 have forgotten too. 



In "Nights with a three-inch Telescope," in Fig. 5 the smaller 

 star should be at the bottom. In Figs. G and 7 the rings of Saturn 

 and the disc of Jupiter are grey in the engraving. The rings and 

 all Jupiter's disc not covered by belts should bo while. The small 

 star beneath t Persei, also in Fig. 8, is to the left of a perpendicular 

 let fall from its primary, instead of slightly to the right of it. 



A Fellow of the Koval Astronomical Society. 



CHEAP TELESCOPES— SUXLIGUT OX FIRES— TEMPERA- 

 TURE OF INTERSTELLAR SPACE— ICE— TIME OF THE 

 GLACIAL EPOCH— UEAT FROM THE STARS. 



[208]— If "R. I. P." (query 135, p. 188) will take my advice, he will 

 make no attemj)! to construct any telescope, cheap or dear, himself. 

 At any rate, five guiuc.is woidd bo the lowest price at which he 

 Could obtain anything whatever worth looking through, and that 

 would not be a wearines.s to the flesh. I presume that by 2J" and 

 3" he means 2 J and 3 inches respectively; but" really signifies 

 seconds of arc, and, legitimately, nothing else whatever. 



"N." (([uery 136, p. 188) may rest assured that it is a mere 

 vulgar superstition that bright sunlight interferes with combustion. 

 It renders flame almost invisible, and so gives an ordinary fire the 

 aspect of going out ; but anyone who will take the trouble to shut 

 the shutters will see at once that the seemingly decaying fire is 

 burning as brightly as ever. As for cigars, I can not only always 

 keep one alight, but never, to my recollection, has one gone out, "in 

 brilliant sunshine. 



In ausAver to query 139 (p. 188) estimates of the temperature of 

 interstellar space not unnaturally differ considerably. Hopkins's 

 was - 39-5 deg. centigrade (No. 15, " Monthly Noticosj" Vol. XVII., 

 p. 192, Fowncs estimated it at -50 deg. cent., and Pouillet as low- 

 as — 112 deg. cent. These are all mere deductions from theoretical 

 considerations, as of course the temperature of space has never 

 been actually measured. 



One single fact will suffice to show that ice (Query 140) does not 

 vary in volume, as other solids do, with variation of temperature ; 

 since it contracts during liquefaction. 



There can be very little doubt that Dr. Croll's Theorj- (Query 141) 

 is substantially correct. No other theories exist which are worthy 

 of scientific attention. Adhcmar's is worthy of Jules Verne ; while 

 Colonel Drayson's — well, his is worthy of Adhemar. 



It may interest " Student " (Qucry'lCl, p. 211) to hear that Mr. 

 E. J. Stone, the present RadclifEe Observer, in 1860 determined the 

 heating effect of Arcturus to amount to 0.00000137 deg. Falir., 

 about equivalent to that radiated by a 3-inch Leslie's cube of boiling 

 water 100 yards off! Curiously the heat from n Lyne is less than 

 this ; in fact, it is only equal to that emitted by a 3-inch cube of 

 boiling water at a distance of 600 yards. 



A Fellow of the Royal Astronojiical Society. 



INTELLIGENCE IN ANIMALS. 



[209J— A pony belonging to a gentleman in this neiglibourhood 

 showed great unwillingness to carry any one on his back. One 

 day ho w as being ridden by a young lady ; he seemed to be very 

 spirited, and galloped along the drive at a good j)ace for some 

 distance, when ho suddenly stopped, stretched out his neck and 

 threw the la<ly over his head. 



For some time after this he was not ridden, but tlio fright gradually 

 wore off, and hia back was once more called upon to bear the 

 burden, until the following incident occurred, after which I don't 

 know what became of him. He was trotting briskly along the 

 road with his young master on his back, when, on coming to a 

 shallow ])ond on the right-hand side of the road, he abruptly 

 turned at riijhl unglit, took a step or two into the pond, then came 

 to a stand, throwing his rider into the centre of it. Ho stood for 

 a moment and looked at his unseated rider, then trotted quietly 

 home. 



1 don't know whether this will bo considered reaeonin<j or not. 

 The pony seems to have thought that if he got off for so long bv 

 throwing his rider on the ground, he might get off for a longer 

 lime if he tlircw him in the pond ; certainly he must have con- 



sidered it more disagreeable to bo thrown into the pond than on to 

 the ground, seeing he turned into the pond to accomplish it. 

 Edinburgh. j. B. 



ASTRONOMICAL CURIOSITY :— EVOLUTION. 



[210] — I have seen somewhere the following paradox, aa I 

 suppose I must call it. Granting (1) that the stars are on the 

 average as bright as our sun, (2) that their number is practically 

 infinite, and (3) that light travels without loss (all of which premises 

 appear to mo perfectly reasonable) j it follows that the sky 

 should always be aa bright as if full of suns, and square suns, so 

 as to fit closely. For a star's greater distance is compensated by 

 the greater number that can shine near together, and the theory 

 supposes that in any direction we should reach stars sooner or later. 

 This result is, however, so different from reality, that I should be 

 glad to be shown where the fallacy lies. [In our next. — Eo.] 



I venture to point out to Mr. Doabarand (Letter 183), first, 

 that biologists should no more be expected to account for the 

 origin of any " first-bom animal," than that astronomers should be 

 called upon to point to the origin of the nebulous globe, from which 

 our solar system is derived, or theologians to explain %vhcnce came 

 the material from which it was made (since we are told that 

 " created " means " set in order"). Secondly, Pasteur, or any one 

 else, has never disproved the possibility of "spontaneous genera- 

 tion ; " all he proved related to| his particular experiments, and 

 similar ones. How do we know, for instance, that, even noir, tbe 

 process is not going on in our ponds and ditches, side by side, if 

 yon like, with the known modes ? It is not possible to disprove a 

 thing like this, and the probability of it must remain a matter of 

 opinion. Thirdly, is it more astonishing that a fish should develope 

 into a reptile by continuous slight modifications, in course of ages, 

 than that a tadpole should become a frog, in the same individual, 

 in a few hours ? I think Mr. Donbavand should read Haeckel's 

 '■ History of Creation," if he still feels interest in the matter. 



Lewis Ari."XDEL. 



LIQUIDS AND THEIR VAPOURS. 



[211] — At what Mr. M. Williams has described (see Kso'sledoe, 

 No. 8) as the "critical temperature" of liquids, the mysterious dis- 

 appearance of all visible distinction between the liquid and its 

 vapour, is much misunderstood by many persons, who imagine that, 

 when this temperature is arrived at, " the whole of the remaining 

 liquid is suddenly converted into vapour." 



W^e know that liquids expand (becoming lighter) as their tem- 

 perature is raised, and, at the same time, the density (and elastic 

 force) of their vapours increases at a very rapid rate, so that we 

 might reasonably expect that, after a certain increase of tempera- 

 ture, the densities of the liquid and of its vapour would become 

 equalised, and at this point, of course, the eye could no longer 

 perceive any distinction between them. This, then, is " the critical 

 state," which thus loses its " mystery." [Not quite. — Ed.] 



No experiments, so far as I am aware, have been instituted with 

 the object of testing this view. But some of those by Cagniard de 

 la Tour (as in the following table) plainly point to the result I havo 

 mentioned above as regards " ether " (See Miller's " Chemical 

 Physics," 1867, p. 306). 



T m lerature Pressure in atmospheres of the vapour of ether. 



F 1 ei 1 e't Volumeof liquid = 7 ; Volume of liquid = 3J. 



„ of vapour = 20. ,, of vapour=aO. 



On increase of temperature, as abovc, = 67°'5 (from 257' to 324°'5), 

 the pressure (in each column) is more than doubled ; whereas, with 

 same increase of tempoi'ature = 67°'5 (from 302° to 369°'5), the 

 pressure is more than doubled (by 7i° atmosphere) in the first 

 column, while in the second column it is !i'S,< than double pressure 

 by thrce"atmosphercs. Hence, the conclusion that in tlie latter case, 

 nil the liquid having passed into vapour, the full pressure was not 

 attained ; whereas, in the former case, where some of the liijuid 

 still remained (though imi>erceptible), the tension continued to 

 increase from addition of vapour, density of both liquid and vapour 

 increasing equally with increase of temperature. 



It would he desirable, if possible, to ascertain (by si>ectroscopeor 

 transmitted polarised light) if any " molecular change of arrange- 

 ment or of motion " could be detected in these different state's of 

 liquid and gas co-existing at the same density. 



Henry Hviisox, M.D. 



