Sept. 21, 1876] 



NATURE 



449 



ithic, but never in beds yielding neolithic implements. As we 

 travel northwards, say to Hessle, these Cyrena-h^rm^ gravels 

 are seen to underlie boulder-clay newer than the upper one 

 of East Anglia ; and in cave deposits still further north, beds 

 yielding the same pleistocene mammals appear in similar situ- 

 ations, notably in the Victoria Cave at Settle. Now bearing in 

 mind that in East Anglia, &c., where these beds are best deve- 

 loped, there has been no subsequent glaciation to sweep them 

 bodily away, or show their age relatively to the glacial epoch, it 

 seems to be a legitimate deduction that they are of inter-glacial age, 

 when we find that to the north, wherever fragments have escaped 

 destruction, they are overlaid by glacial beds. This is the con- 

 clusion to which Mr. Tiddeman arrived from a study of the 

 Victoria Cave deposits and an intimate acquaintance with the 

 glacial phenomena of the district, and my own work in the 

 Fenland and East Anglia led me to a similar result. Mr. J. 

 Geikie has, however, done more than any one to develop this 

 idea, and was the first to propound it. He claims, then, that no 

 paloeolithic implement is of post-glacial date ; and when we 

 reflect upon the vast changes which have occurred since pal-e- 

 oHthic times in the physical configuration of the country, in the 

 mammalian fauna— changes which are even impressed upon the 

 stable molluscs— the theory appears more than probable, and the 

 difficulties which surround the post-glacial hypothesis steadily 

 increase. 



Palaeolithic implements, however, are not all of one age (it 

 would be strange indeed if they were), though it is very difficult 

 to discriminate their relative antiquity. I have been much struck 

 with the aged aspect of certain of the ruder tools as compared 

 with some of the better finished ones and with the stones in the 

 gravel in which they occur, and this gave me hopes of tracing 

 such tools to an older deposit, a desire which has been abundantly 

 fulfilled, and remarkably confirms my friend Mr. J. Geikie's bold 

 surmise. 



Here and there along some of the minor valley sides around 

 Brandon are preserved patches of brick-earth, which are valuable 

 as affording the only workable clay in the district. Whenever 

 these beds are well exposed they are seen to underlie the chalky 

 boulder-clay. Of this there cannot be the slightest doubt, for 

 the glacial bed is typically developed and not in the slightest 

 degree re-constructed. In these beds I have been so fortunate 

 as to find palaeolithic implements in two places ; and in one of 

 them quantities of broken bones and a \&v{ fresh-water shells. 

 The implements are of the oval type, boldly chipped, but with- 

 out any of the finer work which distinguishes the better made 

 paleolithic implements. Although it would be rash to lay too 

 great a stress upon the characters of these implements, it is, 

 nevertheless, worthy of remark that they do belong to the 

 crudest type. Equally rough specimens are found in the gravels 

 above the boulder-clay and even among neolithic finds, still these 

 very antique implements certainly do seem to belong to an earlier 

 stage of civilisation if we regard them as examples of the best 

 workmanship of their makers. 



The interest attaching to these specimens lies in their exceed- 

 ing antiquity— an antiquity greater than can be ascribed with 

 certainty to any others. I have shown this boulder-clay to 

 belong to the earlier part of the ice age, and beneath it these 

 tools were found. I am not yet certain whether they belong to 

 the so-called " middle glacial " series of Mr. Searles Wood, jun., 

 to a somewhat newer date, or to a preceding period, for the beds 

 he directly upon the chalk. This much, however, is certain, that 

 , they conclusively prove man to have been a denizen of our land 

 before the culmination of the glacial epoch. 



Another point is deserving of notice. The tools are decidedly 

 of palaeolithic aspect— the difference between them and those 

 which overlie the boulder-clay is slight in comparison with the 

 differences between the latter and neolithic implements. Who 

 shall say how long East Anglia was swathed in ice? Yet that 

 interA'al was not long enough for man to advance greatly in his 

 manufactures, and it appeais to me we have here another argu- 

 ment in favour of the glacial age of all palaeolithic tools and 

 against the theory which relegates them to after the close of 

 the ice age. It seems to bring the brick-earth tools and the 

 gravel implements closer together, and withdraw them still 

 further from the newer stone age. 



As soon as the bones are examined and the survey of the 

 brick-earths completed, I hope to write more fully upon this 

 question, and here only indite a few preliminary notes in the 

 hope that they may prove interesting to brother geologists. 



Sydney B. J. Skertchly 



The Inverse Rotation of the Radiometer an Effect of 

 Electricity 



In my communication published in Nature, vol xiv p 288 I 

 endeavoured to show that the direct rotation of the radiometer 

 was an effect of electricity. Before attempting to explain the 

 inverse rotation it will be necessary to expound briefly some new 

 tacts which my electroscopic researches have led me to establish. 

 In order to ascertain the electric state of their inner surface, I 

 exposed to solar radiation glass receivers such as are used for the 

 air-pump. By means of the proof plane and electroscope I 

 found that this surface was electrified negatively, and even to a 

 greater degree than the exterior. This excess of energy I attri- 

 bute to the numerous reflexions from the interior. If however 

 we hold one of these electrified receivers near the Bohnenberger 

 electroscope, taking care that it does not come in contact with 

 It the electroscope at once indicates the presence of positive 

 e ectncity. As both the outer and inner surfaces are negatively 

 electrified, this phenomenon must be attributed to the electr-city 

 developed in the interior of the glass itself by its molecular 

 polarisation and feeble conductivity. The following experiment 

 confirms this explanation. If we remove from the exterior by 

 means of the proof-plane a portion of the negative electricity 

 and then approach, as before, the globe to the electroscope a 

 remarkable increase of positive electricity is at once shown. The 

 same results are observed in the radiometer. 



I next examined the electric state of the exterior of the radi- 

 ometer globe when placed in partial obscurity and moistened 

 with ether. There are no signs whatever of electricity as long 

 as the inverse rotation continues, but as soon as the direct rota- 

 tion commences— on account of the obscure radiations given forth 

 by the surrounding bodies— positive electricity manifests itself and 

 rapidly increases. While in this state I exposed the radiometer 

 to solar radiation, and I found that this positive electricity re- 

 mains quite a long time, and that, notwithstanding the positive 

 charge on the exterior, the direct rotation continues with its 

 usual rapidity. 



The fact last-mentioned enabled me to determine, by experi- 

 ment, the electric state of the inner surface of the radiometer 

 globe. Only two suppositions can be made in regard to it • 

 either the electric state of the inner surface is dependent by 

 means of molecular polarisation upon the electric state of the 

 exterior, or it is independent. In the first supposition the in- 

 terior face is electrified positively when the exterior is electrified 

 negatively, and zice versd. The second supposition may be 

 divided into three hypotheses, for we can admit that the interior 

 IS constantly, under the same circumstances, either neutral, or 

 negative, or positive. Hence we have in all four hypotheses 

 a prion, viz. : — 



1. Inner surface is dependent upon electric state of exterior. 



2. Inner surface is independent and neutral. 



3. Inner surface is independent and negative. 



4. Inner surface is independent and positive. 



Now of these four hypotheses the fourth alone is verified by 

 experiment. This I have established as follows :— 



In one series of experiments I charged the exterior of the 

 radiometer with positive electricity by exposing it to solar 

 radiation. 



In a second series I charged the same surface with positive 

 electricity by exposing it to solar radiation after moistenine it 

 with ether. ** 



Each experiment comprised two operations. I touched a cer- 

 tain number of times the exterior of the glass globe with the 

 proof-plane and I carefully observed the electroscopic signs of the 

 Bohnenberger electroscope when brought in contact with the 

 proof-plane ; then I approached to the electrometer the glass 

 globe which had been partially discharged by the preceding 

 experiment, and I again observed the signs given by the electro- 

 scope. In the case that one of the first two hypotheses ex- 

 presses the real state of the inner surface of the radiometer under 

 the influence of radiation, on approaching the glass globe we 

 should have, in both series of experiments, electroscopic signs of 

 equal intensity for equal electric charges of the exterior surface, 

 manifested by the equality of those of the proof plane. Now 

 this does not take place. In my experiments on the approach 

 of the globe the electroscopic signs in the second series surpass 

 in intensity those observed in the first series. These results agree 

 perfectly with the fourth hypothesis, but are in open disaccord 

 with the third. Any one can easily see this, with a little atten- 

 tion, by considering the layers of electricity produced in the 

 mterior of the glass walls by molecular polarisation. The fourth 



