Mar. 5, 1874J 



NA TURE 



345 



whatever, in which the law of statistical constancy pre- 

 vails, the series, in each case, being arranged accord- 

 ing to gradations of the quality in question. Each 

 individual is measured against his neighbour, and it 

 is quite unnecessary to have recourse to any ex- 

 • ternal standard. As regards a scale of equal parts, 

 the lecturer made use of a converse application of the 

 law of "fiequency of error," which he illustrated by 

 many experiments, and which sho'ved that in a row (say 

 as before) of nuts, if we took those which occupied the 

 three quaitcrly divisions (rst quarter, centre, 3rd quarter) 

 as the three elementary graduations of size, a range of 

 successive graduations would be obtained by the follow- 

 ing sciies, in which the places of the nuts are supposed 

 to be reckoned from the end of the row where the large 

 nuts are situated, and to be given in per-thousandths of 

 the entire length of the row. It might be called the 

 "Common Statistical Scale" (S. S.). The place of + 4" 

 would be at 4 thousandths from large end ; +3°, at 21 

 thousandths ; -|- 2° at 89 ; + i, at 250 ; 0° at 500 ; - i" 

 at 750 ; — 2° at 91 1 ; - 3° at 979 ; and - 4° at 996, or 4 

 thousandths from the small end of the row. Thus if we 

 say that the size of a nut is + 2° S. S., we absolutely de- 

 fine it. Anybody can procure such a nut independently 

 by getting a quart of nuts and arranging them. 

 Also we know that the ditTeience between a nut of 

 -j- 4° S. S. and + 1° S.S. is 3', and therefore three 

 times as great as between one of -)- 2° S. S. and the 

 latter. It cannot be affirmed that this is a precise 

 scale of equal parts for all qualities, but it is found to 

 hold surprisingly well in a great variety of vital statistics ; 

 perhaps, too, the mere thickness of tissues may be a chief 

 clement in the physical basis of life. This scale appears, 

 at all events, more likely to be nearly approximative 

 to one of equal parts, for qualities generally, than any 

 other that can be specified, and it certainly afi"ords defi- 

 nite standards subject to the law of statistical constancy. 

 The habit should therefore be encouraged in biographies, 

 of giving copious illustrations which tend to rank a man 

 amorg his contemporaries, in I'espect to every quality 

 that is discussed, in order to give data for appraising 

 those qualities in ter-ms of the .Statistical Scale. By the 

 general use of a system of measurement like the above, 

 social and political science would be greatly raised 

 in precision. 



Regarding education, the lecturer disavowed speaking 

 of what might be suitable for boys generally, but he sum- 

 marised the replies of the scientific men with referer/ce 

 to their own special experience, and notwithstanding the 

 diversity of branches of science, he found unanimity in 

 their replies. They commonly expressed a hatred of 

 grammar and classics, the old-fashioned system of educa- 

 tion being utterly distasteful to them. The following seems 

 the programme they themselves would have most liked : — 

 I. Mathematics, rigorously taught up to their capacity, 

 and copiously illustrated and applied, so as to throw as 

 much interest into its pursuit as possible. 2. Logic. 3. 

 Some branch of science (observation, theory, and experi- 

 ment), some boys taking one branch and some another, 

 to insure variety of interests under the same root'. 4. 

 Accurate drawing of objects connected with that branch 

 of science. 5. Mechanical handiwork. All these to be 

 rigorously taught. The following not to be taught 

 rigorously : reading good books (not trashy ones) in lite- 

 rature, history, and art. A moderate knowledge of the 

 more useful languages taught in the easiest way, probably 

 by going abroad in vacations. It is abundantly evident 

 that the leading men of science have not been made by 

 much or regular teaching. They craved for variety. 

 Those who had it, praised it ; and those who had it not, con- 

 curred in regretting it. There were none who had the old- 

 fashioned high-and-dry education who were satisfied with 

 it. Those who came from the greater schools usually did 

 nothing there, and have abused the system heartily. 



INFLUENCE OF GEOFOGICAL CHANGES ON 



THE EARTH'S ROTATION 

 A T the annual meeting of the Geological Society of 

 -^ *• Glasgow, on Feb. 12, the president. Sir William 

 Thonison, F.R.S., gave an address on the above subject, 

 of which the following is an abstract : — 



He first briefly considered the rotation of rigid bodies 

 in general, defining a principal axis of rotation as one for 

 which the centrifugal forces balance while the body re- 

 lates around it. He then took the case of the earth ; and, 

 having pointed out the position of its present axis, showed 

 that if from any cause it were made to revolve round any 

 other, that would be an "instantaneous axis," changing 

 every instant, and travelling through the solid, from west 

 to east, in a period of 296 days round the principal axis 

 It would shift continually in the figure, owing to the vary- 

 ing centrifugal force of two opposite portions of the bod)-. 

 This would produce, by centrifugal force, a tide of peculiar 

 distribution over the ocean, having 296 days for pcrioc. 

 An iiiclination of the axis of instantaneous rotation to 

 principal axis of 1", or 100 ft. at the earth's surface, 

 would produce rise and fall of water in 45° latitude, where 

 the effect is greatest, amounting to -17 of a foot above and 

 below mean level. 



He noticed, in passing, the application of these 

 dynamical principles to the attraction which the sun and 

 moon exercise on the protuberant parts of the earth, 

 tending to bring the plane of the earth's equator into coin- 

 cidence with the ecliptic. This causes an incessant 

 change, to a certain limited extent, in the position of the 

 axis of rotation, thereby occasioning what is known as 

 the "precession of the equinoxes." Having illustrated 

 these i-emarks by some interesting experiments, SirWilhani 

 Thomson proceeded to consider more particularly the cir- 

 cumstances according to which the axis of the earth 

 might become changed through geological influences, and 

 the consequences ot any such change. The possibility of 

 such a change had been adduced to account for the great 

 differences in climate which can be shown to have ob- 

 tained at different periods in the same portion of the 

 earth's surface. In the British Isles, for example, and in 

 many other countries, there is clear evidence that at a 

 comparatively recent period a very cold climate— much 

 colder than at present — prevailed ; while in the same 

 places the remains of plants and animals belonging to 

 several preceding eras indicate a high temperature and a 

 comparatively tropical climate. The question arose, can 

 changes in the earth's axis account for these changes of 

 climate.^ In the present condition of the earth, any 

 change in the axis of rotation could not be permanent, 

 because the instantaneous axis would travel round the 

 principal axis of the solid in a period of 296 days, as 

 already stated. Maxwell had pointed out that this 

 shifting ofthe instantaneous axis in the solid would con- 

 stitute in its period a periodic variation everywhci'e of 

 " latitude," ranging above and below the mean value, to 

 an extent equal to the angular deviation of the instan- 

 taneous axis of rotation from the principal axis ; and, by 

 comparing observations of the altitude of the Pole-slar 

 during three years at Greenwich, had concluded that 

 there may possibly be as much as i" of such deviation, 

 but not more. 



Ill very early geologic ages, if we suppose the earth to 

 have been plastic, the yielding of the surface might have 

 made the new axis a principal axis. But certain it is that 

 the earth at present is so rigid that no such change 

 is possible. The precession of the equinoxes shows that 

 the earth at present moves as a rigid body ; and during 

 the whole period of geologic history, or while it has been 

 inhabited by plants and animals, it has been practically 

 rigid. Changes of climate, then, have not been produced 

 by changes of the axis of the earth. The learned pro- 

 fessor then inquired what influences great subsi-'iii'^e? si 



