Nov. 



ISSl.] 



K N GwV 'LKDGE. ♦ 



77 



the sun. It seems to me that the matter is of far greater com- 

 plexity than your corresponilent imagines. — Yours, &c., Veras. 



[36] — Yonr correspondent " Anti-Guebre " (p 15, Xo. 1) takes 

 up rather a large amount of what I expect in future will be 

 very valnable space, with his question as to whether the sun is hot, 

 and in proof that it is not so, he brings forward the apparent fact 

 that as we ascend high mountains we get cooler. This, however, is 

 not exactly a fact, and it is very difficult to convince the unscientilio 

 public that it is not so, as I found to my trouble during a twenty 

 years' residence as a medical man in India. Now the amount of 

 heat which we are sensible of on a hot day does not come ta the 

 body directly or entirely from the sun, but from the earth, which 

 has been heated by the sun's rays. In the hills (I refer more 

 especially to tropical countries), the heat received by the soil 

 during the day is radiated to such an extent during the night, that 

 the surface becomes thoroughly cooled down. In the plains below, 

 probably from the greater density of the superjacent air, the i-adia- 

 tion is very small, and the heat is retained, to be added to by the 

 succeeding day's sun. The movement of currents of air, also, is 

 much more constant in the hills, and this acts like a fan in con- 

 tinually changing the air which has become heated by contact with 

 the surface of the earth. The heat received directly from the sun 

 should, of course, increase the higher we ascend, not because we are 

 a few thousand feet nearer to it, but because so much less of its 

 power is absorbed by the lower and denser layers of the 

 atmosphere. And so it does, as is proved by the fact, not 

 so generally known, that the black bulb thermometer indi- 

 cates the increased temperature as the elevation increases. The 

 readings of this at Ootacamund, in South India, average about 11° 

 above those tak?n simultaneously at the coast towns. I have re- 

 peatedly noticed that Europeans who come from the low country up 

 to the hill sanitaria, while enjoying the cool atmosphere, yet had 

 their faces completely peeled by the increased diiect action of the 

 sun's rays. I have seen a child's hat blown off, and before it could 

 be picked up again the child was stricken down by sunstroke, and 

 this at a time when there had been ice on the plain during the 

 night, and I have always noticed that while it was possible to walk 

 short distances in the sun in the low country with an ordinan* green 

 silk umbrella, yet that at six or seven thousand feet elevation this 

 became quite insufficient, the heat seeming to strike right through 

 it, at once rendering the addition of a white calico covering abso- 

 lutely imperative. B. M., F.R.C.S. 

 -Vor. 18. 



[37] — In letter 2, page 15, your correspondent says that "the 

 sun is not himself hot'; but, of course, he is the sotirce of heat to the 

 earth." How does he reconcile the two statements ? He might as 

 well maintain that his fire, which he nses as a conclusive proof to 

 himself of the non-incandescence of the sun, is not in itself hot, 

 though it is a source of heat to things snrounding it. He also uses 

 that question which has been so often advanced by inquirers, and 

 as often replied to by scientists, Why is it that the higher you go 

 from the earth the colder it becomes, if, as people say, the sun be 

 hot ? He foi-gets the important part the atmosphere plays with 

 regard to our earth. I maintain that the nearer the earth is to the 

 sun, not the nearer we get up through our atmosphere to it, so the 

 heat transmitted becomes greater. When the earth is at its perigee, 

 the sun transmits more warmth than when it is at its apogee. To 

 this he may advance the argument that the perigee occurs in 

 January. .So be it. From this very cause winters are milder and 

 summers cooler in the northern than in the southern hemisphere. 

 Then, as he says the sun is not hot, can he erjilain why the earth 

 should derive more heat from the sun when its rays fall vertically 

 than when they fall obliquely ? If the source of heat be contained 

 in the earth itself, then should the poles be warmer than the 

 equator. We know the opposite to be the case. In Letter 5, 

 page 35, your correspondent says, " Light and heat are surely phe- 

 nominal products, caused by magnetic and electrical forces in a 

 state of intense activity." If so, why is there greater heat when 

 the sun's rays are vertical, if it has nothing to do with the produc- 

 tion of heat ? In this letter there is more dealing with probabili- 

 ties than with facts. Probabilities do not exist in Nature, and I 

 trust that through your columns we may arrive at a clearer idea of 

 the truth concerning this question of the sun's heat. I hardly see 

 that Letter 6 requires an answer, as this is not so much a question 

 of light as of heat. — Yours, verv faithfully, G. G. D. 



Xov 15, 1881. 



Posd's Eitbact is a certain 



Pond's Extract is a certain ci 



Pond's Extract is a certain ci 



Pond's Extract wiU heal Bums and Wo 



Pond's Extract will cure Sprains and Bruises, 



Sold hy all Chemists. Get the genuine. 



re for Bhenma|ri9m and Gout, 

 for Hemorrhoids (PilesJ. 



for Xeuralgic pains. 



[Al>VT. 



STAR NAMES.— COMETS' TAILS. 



[3S] — May I suggest, in regard to your excellent star maps, that 

 it might be some ini])rovement to them if the names of well-known 

 stars, such as Capella, Aldebaran, &c., were marked in the map, as 

 well as the name of the constellation and the o, /?, y, Ac. ; or, at 

 least, attention might suitably be called to them in a note naming 

 the brightest star in each particular map. 



I have annotated your first map for the benefit of my boys, 

 writing at the side — 



Aldebaran = a Tam-i, 



Rigel = ft Ononis, &c., &c. 



No explanation I have yet heard as to the material, &c., of 

 comet's tails appears very satisfactory. Has the idea ever occurred 

 to you that a comet repels matter from its nucleus in the form of 

 vapour, or a highly-attenuated condition of solid particles, not in one 

 direction only, but lateraUij as well ? And that wo might only see 

 the portion of this matter through which a ray of light was pro- 

 jected from the sun or from the glowing mass of the comet itself, 

 at such an angle as to render its path visible to us in the same 

 manner as we see snn-rays at stmrise and sunset, or when the sun 

 is emerging from a cloud ? 



Would not this account for the apparently incredible rapidity 

 with which comets' tails swing round the stm at perihelion, and 

 also for comets, when distant from the sun, not exhibiting any tail 

 at all ? 



There are other points I wished to mention, but have not time 

 to-night. I heartily wish your excellent paper every success, and 

 am, yours faithfully, Speculum. 



PRACTICAL WORK WITH THE TELESCOPE.— MAP OP 

 EASTERN SKIES. 



[39] — I am verj- much pleased with the first two numbers of 

 K.NOWLEDGE, and I am doing all I can to make it known amongst 

 friends. I have had some difficult}' in getting the numbers, but 

 perhaps this will be all right hereafter. 



I have been a " star-gazer" for a few years, and have read a good 

 many of the treatises on astronomy, but have never been able to 

 turn my knowledge into any practical shape. If you could throw 

 out a few hints as a guide for those desiring to start in this study, 

 I think they would be of great service. What particular branch 

 would you recommend to start vrith, and how ought the study to 

 be carried out ? What handbooks and instruments would you 

 recommend ? 



Surely there is some mistake in your map of the eastern sky 

 issued with No. 1. In yotir map you place Saturn highest above 

 the horizon, then Jupiter, then the Pleiades ; whereas the reverse is 

 the order, Orion is placed verj- much on its side, and so on. 

 Wishing vou every success, I remain, veurs, &c., 



Ediubtirgh, yoc. 16, 1881. " G. M. 



[With reference to the last question, has " G. M." understood 

 that the circtdar outline of the map is the horizon ? Thus it must 

 be held with the word south-east lowest to show the position of the 

 objects he names, which all lie, speaking generally, towards the 

 south-east at the hom- corresponding to the map. Note, however, 

 that by an unfortunate error, corrected in part of the present issue, 

 the hours named under the maps in Nos. 1, 2, and 3 are all, without 

 exception, one hour too late. This should be corrected in each 

 map, as t'.e maps, apart from the planets shown, will be as correct 

 for next year, or for twenty years hence, at the same dates, as for 

 the present year. — Ed.] 



CELESTIAL OBJECTS. 



[10] — I have obtained the first two Nos. of Knowledge, and am 

 much pleased with the contents; the star maps especially I was 

 veiy pleased to see. Would it be in accordance with j'our plans to 

 publish, from time to time, a few notes descriptive of interesting 

 and remarkable objects in the constellations? Several of my friends 

 to whom I have shown Knowledge have promised to become 

 subscribers ; and to those of us who dabble a little in astronomy, 

 the name of the Editor is a sufficient guarantee of the information 

 we shall get on that subject, at any rate. Wishing Knowledge the 

 success it deserves, — I remain, yours, ic. W. J. C. 



ARE WOMEN INFERIOR TO MEN ? (Ahstract.) 

 [41] — I perused with some interest in the first issue of your 

 paper an article on the question whether women are inferior to 

 men. The study of the human mind and character seems to bo 

 neglected by most publications, although it is a most interesting 

 subject. I am sure if you will open your columns for such subjects, 

 you will not fail to gain appreciative and constant readers. The 



