FOR GENERAL READERS. 



Vol. I. — No. 25. {New Series.) 



FRIDAY, JUNE 22nd, iJ 



r Weekly, Price Sd. 

 L By Post, SJd. 



CONTENTS. 



PAGE 



Scientific Table Talk 577 



The First Geological Maps 578 



Proposed High-L'.vel Bridge for Am- 

 sterdam {illus.) 579 



What is a Generalised Portrait ? ... 580 



Remarkable Hailstones (illus.) ... 581 



The " Egyptian " Argument 582 



General Notes 583 



Intelligence of Insects (zV&j-.) ... 585 

 Experiments in Capillary Attraction 



{ilhis.) ... 585 



New IMethod of Nature Printing ... 586 

 Natural History : 



Arborescent Euphorbia (illus.)... 587 



PAGE 



Sieve Tubes ... ... ... 588 



Weaver Birds and their Nests ... 588 



Spread of the Starhng 588 



Miscellaneous Notes 588 



Austrahan Mammals 589 



Reviews : 



The Reason Why 590 



A Catalogue of the Molhs of 



India — Part 1 591 



Tropical Africa ... ... ... 591 



A Manual of Phonography . . . 592 



Abstracts of Papers, Lectures, etc. : 



Geological Society 592 



Royal Horticultural Society 

 Liverpool Geological Association 



Social Condition of the Babylonians 



The Causation of Vital Movement 



Mesmerism 



Correspondence : 



A Circle Problem — The Quantity 

 of Life 



Recent Inventions 



Announcements 



Diary for Next Week 



Sales and Exchanges ... 



Selected Books ... 



Meteorological Returns 



PAGE 



594 

 594 

 594 

 596 

 597 



598 

 598 

 599 

 599 

 600 

 600 

 600 



SCIENTIFIC TABLE TALK. 



By W. Mattieu Williams, F.R.A.S., F.C.S. 

 Naturally connected with my last is a very interesting 

 question that has been much discussed, viz., whether the 

 inclination of the earth's equator to the plane of the 

 earth's path around the sun has been, or may be, 

 materially changed. As we all know, this inclination 

 now amounts to 23* degs. (23 degs. 28 mins.), or, other- 

 wise stated, the axis of the earth does not stand upright 

 at it proceeds around the sun, but leans over to the 

 extent above-named. Has this leaning over ever been 

 greater or less ? May it hereafter become greater or 

 less ? These are the questions to which I refer, 

 neglecting altogether the well-understood and undisputed 

 actual elliptical oscillation or nutation which is of insig- 

 nificant account, and has a recurrent period of about 19 

 years. 



I need scarcely add that to the leaning of the earth's 

 axis, and its persistence in leaning in the same direction 

 throughout its annual journey, we owe all the pheno- 

 mena of changing seasons, as each hemisphere must 

 during one-half of its journey lean towards the sun and 

 during the opposite half be turned to the same extent 

 away. 



Geological phenomena indicating great changes of 

 climate in given parts of the earth, which otherwise are 

 not easily accounted for, present strong temptations to 

 speculate upon changes in the inclination of the earth's 

 axis. Two kinds of such change have been imagined. 

 First, that the position of the axis relatively to the earth 

 itself has changed, / c, instead of rotating as at present 

 equally around an imaginary line extending from 

 the present north to the present south pole, it has rotated 

 about some other line, changing the position of the poles 

 accordingly. 



This hypothesis is so violent that it scarcely needs 

 discussion. If the earth were a perfect sphere and 

 perfectly rigid, such instability of axis might be a fair 

 subject for consideration, but the earth being a spheroid 

 «f rotation the whole mass of its equatorial protuberance 



resists the change, and must either be transferred to the 

 new equatorial region, or it would be continually acting to 

 restore the old position should any great internal commo- 

 tion change it. Such a change as supposed involves a 

 breaking up of the earth, a transfer of its oceans and 

 rupture of its crust, by earthquakes exceeding in mag- 

 nitude the greatest of those indicated by geological 

 phenomena. 



The other idea is that the earth, as a whole, may have 

 tilted a little, the poles and equator remaining the same 

 so far as the earth itself is concerned, but the apparent 

 daily path of the stars changing on account of the 

 difference of direction of the actual rotation of the 

 earth. 



The possibility of this is stoutly denied by the majority 

 of a3tronomers. They are not, however, unanimous. I 

 was present at the Dublin meeting of the British Associa- 

 tion when it was proposed to conclude the meeting of the 

 geological section with a "Donnybrook" on this subject, but 

 unfortunately time did not permit. It is not my present 

 intention to wield a shillelagh on either side, but by giving 

 rein to the imagination to discuss the instructive question 

 of what would happen, if, by some internal shifting or 

 external impulse, the earth should swing through 23I 

 degs. and its axis of rotation stand upright in reference 

 to the path of its revolution about the sun. 



We should then, as regards the incidence of the solar 

 radiation, be permanently in the position we now occupy 

 at the periods of the vernal and autumnal equinoxes, 

 at or about 21st March and 21st September. The 

 shadow limit separating day and night would pass per- 

 pendicularly across the equator from pole to pole. 

 Excepting in the polar regions, day and night would be 

 always nearly equal. At the poles there would be ever- 

 lasting daylight. The sun would there be seen as a golden 

 ball bowling steadily round the horizon in twenty-four 

 hours ; due north at the midnight of other places, due 

 south at noon, and due east and west at 6 a.m .and 6 p.m.; 

 he would not appear exactly touching the horizon, but 

 standing a little more than half his own diameter above 

 it. This curious state of astronomical affairs actually 



