,GS 



• KNOWLEDGE • 



[May :,, 1882. 



England nnel Bolgiuni had been explored, but it was not 

 until 1K17 that the 'i'onniay Natural History Society em- 

 bodied the results of their labours in Kent's Hole, in a 

 paper which was sent to the Geological Society. What 

 obtuseness to the momentous revolution in current beliefs 

 JUS to th(! antiquity and primitive state of man which these 

 and like? discoveries involved, the Council of that learned 

 body displayed, is shown in this laconic entry in their 

 (Quarterly Journal, " On Kent's Cavern, near Torquay, 

 in this paper an account was given of some recent re- 

 searches in that cavern Ijy a committee of the Torquay 

 Natural History Society, during which the bones of various 

 extinct animals were found in several situations." 



Nor did they manage these things better in France. In 

 the same year (1817) M. Boucherde Perthes called attention 

 to the discovery of sonic rudely-shaped flint implements in 

 pits which were being worked for sand and gravel in the 

 Somme valley, near Abbeville. They had been found at 

 intervals during the preceding six years in such positions 

 and so far below the surface as to convince him that they 

 were not later, but j^robably much earlier, than the 

 deposits in which they were embedded, and in which were 

 also found bones of the mammoth, woolly-haired rhino- 

 ceros, and other extinct animals. M. de Perthes argued 

 that these worked flints had been fashioned by man, and 

 witnessed to his high antiquity and low level of culture. 

 But he was met with the reply that these so-called tools 

 and weapons were either natural fractures or forgeries, 

 and an account of similar finds of "instruments en silex " 

 in the Drift at St. Acheul (hence the term Acheulian), 

 near Amiens, which was published by Dr. Rigollot in 

 18.5.5, met with the same reception. 



It seems strange to us, with whom the " Origin of 

 Species " has for some years been a canonical work, that, 

 until within the last quarter of a century, even the masters 

 in our scientific Israel were so fettered by traditional 

 opinions concerning man, that they deprecated any re- 

 sistance to these, so that the investigation which he had 

 for a long period extended to the earth beneath him, and 

 for a still longer period to phenomena above him, was 

 applied to his kind and its place in the succession of life 

 last of all. 



A dozen years passed before savants on both sides of the 

 Channel confessed themselves mistaken. In 1858-9, some 

 English geologists, stimulated by discoveries in Brixham 

 cavern, examined M. de Perthe's collection of implements, 

 and the beds in which they were said to have been found. 

 " In addition to being perfectly satisfied with the evidence 

 adduced as to the nature of the discoveries, they had the 

 crowning satisfaction of seeing one of the naked flints 

 still in situ in its undisturbed matrix of gravel, at a 

 depth of seventeen feet from the original surface of 

 the ground."* An impetus was thus given to further 

 research, and not only were discoveries of similar 

 implements (presumably, from their general resemblance 

 of form, of the same age, and shaped by the same race of 

 men), made in England in beds of gravel, sand, and clay, 

 for the most part on the slopes of our existing river-valleys, 

 but it was ascertained that flint implements had been 

 disinterred at the end of the last century from the 

 Waveney Valley, in Suflblk, only to be, as it were, re- 

 interred in the Museum of the Societv of Antiquaries. 

 The earliest known find of a flint in the drift was in the 

 Thames Valley, probably at the close of the seventeenth 

 century. It is said to have been found with the tooth, or, 

 according to another account, the skeleton, of an elephant, 

 near Gray's-Inn-lane, and is preserved in the British 



Museum. It would be easy to convert this paper into a 

 dry catalogue of discoveries, and to avoid that prosaic 

 result, it sulKces to say that implements of stone, — leaf- 

 .sliaped flakes, removed from flints by blows or pres- 

 sure, and apparently intended as knives and scrapers; 

 pointed weapons analogous to lance or spearheads; 

 oval or almond-shaped weapons, with cutting edge 

 all round, — have been found by thousands in the drift of 

 England and the Continent. This river-drift is formed of 

 alluvial dopo.sits bought down by that unresting, yet un- 

 hasting action of rain and flood which is for ever deepening 

 the bed over which the waters flow. Since the time when 

 the men of the Acheulian period lived in France, the 

 Somme has cut down its valley one hundred feet — a result 

 which requires an enormous antitjuity for the flint imple- 

 ments found in the undisturbed gravels. The Vjottom of 

 that valley has yielded polished stone weapons and other 

 remains further illustrating the vast lapse of time between 

 the Ancient and Newer Stone Ages — vast, even after 

 making full allowance for a more rapid action of rain and 

 flood in the Quaternary period than now. 



THE AMATEUR ELECTRICIAN. 



ELECTRIC GENERATORS (Continii>'d). 



IN the previous article we described the first principles of 

 magneto-electricity, and got so far as to say that when 

 an electro-magnetic coil is made to pass across the poles of a 

 permanent magnet, currents of electricity are induced in 

 the coil. These currents are reversed in direction everj' 

 time the coil changes its position in relation to the magnet, 

 that is to say, the current induced as the coil ^^^ "che.s 

 the magnet being in one direction, the current induced after 

 the coil has passed, and as it recedes from the magnet, 

 will be in the opposite direction. Commutators or current 

 reversers are used, by means of which these opposite 

 currents are sent in one common direction through the 

 external circuit. 



The electro-magnetic coil, however, need not necessarilj' 

 be of the orthodox form. JI. Gramme, about 1870, designed 

 a coil (which, by-the-way, is called the armature of the 

 large or field magnets, consisting of a ring of soft iron, 

 with insulated copper wire wound round it in sections. 

 The object in view was to have a part of the coil always 

 passing through the magnetic field, and so to be constantly 

 producing electric currents, instead of only once or twice 

 in each revolution. For an amateur, however, the Gramme 

 machine is comparatively dLfficult to make. 



• Kvann'e " Aiiolont Stone Implenienta," p. 478. 



We prefer, therefore, to describe in detail a machine 

 with what is know as " Siemen's " armature, being much 

 easier to make, and quite sus efficient. This armature 



