September, 1911. 



KNOWLEDGE. 



339 



tion of the great masses of gabbro, and wherever the 

 gabbro is pierced bv the veins a very pecuHar altera- 

 tion is produced in the gabbro which shows that it 

 has been affected by heated waters containing Chlo- 

 rine, a characteristic constituent of the ore apatite. 

 We have thus traced mountain building, the 

 formation of igneous rocks, and the production of 

 mineral \eins, back to the same source — the great 

 crustal movements caused bv the contraction of the 

 cooling earth. Despite their enormous effects, these 



movements are so slow that the}- would escape 

 notice altogether but for those surface symptoms, 

 earthquakes and volcanoes, which remind us that 

 there are jolts in the evenness of an otherwise 

 imperceptible movement. Movements that have 

 begun long before historical times are still un- 

 finished. The Himalayas are even no-w being folded 

 over towards the great plain of India, and the far 

 more ancient Highlands of Scotland are still moving 

 feeblv along the old faults. 



QUERIES. 



Readers are invited to send in Onestions and to ansic-er the Queries ichich are printed here. 



REPLIES. 



46. BIBLE .A.STRONOMY. — I do not know in what spirit 

 J.W.A. has written this query. The sudden standing still of 

 any of the heavenly bodies (apart from collision) is obviously 

 of the nature of a miracle, i.e., the operation of some special 

 agency over and above the ordinary known forces. We clearly 

 do not know its mode of action, so cannot introduce it into 

 our mathematical analysis. But it would obviously be futile to 

 leave out of account the action of this transcendent power, 

 and yet to expect to obtain the true " effect on our planet and 

 others of the system," on the assumption that only the known 

 forces were acting. This is, however, the inconsistent assump- 

 tion that J.W.A. appears to contemplate. Many think that the 

 poetical and somewhat indefinite terms of the narrative can be 

 sufficiently explained without assuming an actual change in 

 the motions of the heavenly bodies. For example, he will find 

 in Mr. E. W. Maunder's "The Astronomy of the Bible," the 

 suggestion that the miracle was really the giving of unusual 

 strength and endurance to the pursuing army, so that they 

 made an afternoon march which would normally be deemed 

 impossible, and inferred that the day had been lengthened. 



A. C. D. Crommelin. 



47. GR.W'lT'i'. — I think it is sufficient to simply say that it 

 is gravitv, and not the atmosphere, which prevents our falling 



°fft*^^^^^'h- A. C. D. Crommelin-. 



47. GRA\'ITV. — The statement made by your correspon- 

 dent's friend. " That gravity is now rather discredited by 

 scientific men " is quite incorrect. 



The theory that '" We do not tumble off the earth because it 

 is surrounded by the atmosphere" is .absurd on the face of it. 

 seeing that the air, like every other substance, has weight and 

 actually tends to buoy us up. Humphrev Wilson. 



QUESTIONS. 



49. POLAR PHENOMENA.— I am thankful to the Rev. 

 Mr. Davidson for enlightening me. in the February number of 

 your journal, on some points of Polar Phenomena which had 

 troubled me for some time past. May I take the liberty of 

 troubling Mr. Davidson again, or any of your readers who may 

 take interest in the matter, to enlighten me on the following 

 points also. 



1. An Indian author in his calendar for S6i- of latitude gives 

 twenty-four to twenty-three days as the period of continuous 

 long dawn, seventeen to eighteen days as the period of alter- 

 nation of twilight and sun, and one hundred and sixty-nine to 

 one hundred and seventy-one days as the period of continuous 

 long day. Are these figures strictly correct, or may I assume 

 that in actual observation they may vary slightly ? I want a 



latitude which would give twenty-four days for the long dawn, 

 sixteen days for the period of alternation and one hundred and 

 seventy-one days for the long day. Will 86^° suffice for my 

 purpose or shall I have to assume it to lie between 864° and 

 87°— say, at 86^° ? 



2. What is the exact manner in which the sun's disc is 

 rendered visible during the sixteen days-long period of alter- 

 nation ? I am told that the period of alternation begins when 

 the South declination is 4° 20', and ends when the North 

 declination is 4° 20'. Shall I be wrong in imagining that the 

 phenomena of sunrise during the alternation period occur as 

 follows ? On the first day the sunshine will last for about 

 one-and-a-half hours only, and the maximum portion of the 

 sun's disc visible that day (at noon) will be about one-sixteenth 

 of the whole. On the second day about a two-sixteenths portion 

 of the disc will rise into %iew, and the day will last for nearly 

 three hours. On the third day three-sixteenths, on the fourth 

 four-sixteenths and so on, till at noon on the sixteenth day, 

 the whole disc will have emerged into view, standing just 

 above the line of the horizon. Of course, the stay of the sun 

 above the horizon will not be in the e.xact arithmetical pro- 

 gression as I have stated above, but practically the progres- 

 sion may be assumed to be so, as the daily variation will be 

 slight. I wish to know if the phenomena occur as assumed 

 above, or whether the complete disc of the sun will be visible 

 at noon, for some days during this period of sixteen days. 



3. If the first day of this alternation period falls on the 

 eighth day of the dark half of a certain month, will not 

 the Vernal equinoctial colure occur on the new moon day 

 following or on the first day of the bright half of the next 

 month ? And also, may not such colure be assumed to occur 

 at the very beginnings of a new (lunar) constellation ? A certain 

 Vedic passage says that the new year's day falls on the eighth 

 day of the dark half of the month connected with the constella- 

 tion Magha. which has been identified with Regulus (129'). 

 Assuming this day to be the first day of the sixteen days-long 

 alternation period, shall I be right in taking the equinoctial 

 colure to occur in (Delta) Leonis (139^ 5S') ? 



I shall thank any one of your readers if they will kindly 

 enlighten me on the above-mentioned points. 



Baroda. 



R.K.P. 



50. RADIO-ACTIVITY.— Would any of your readers 

 inform me concerning the following questions for which I have 

 not been able as yet to find an answer. 



(1) Is it definitely proved that the a particles of a radio- 

 active body are helium ? Is this transformation ? 



(2) What is the exact nature of X rays ? are they identical 

 with and the same as the y rays of radio-active bodies ? 



(3) What is the cause of the glow of the glowworm ? 



H. Sinclair Tait. 



