January 4, 1894] 



NATURE 



227 



of electricity is due to convection currents, and this view 

 has been further strengthened by Righi, who placed a 

 plate of ebonite covered with tin foil on its upper side 

 above a brass plate on which some figure, such as a cross, 

 had been traced with varnish so that theplatewasprotected 

 at these points from the effect of the illumination, the active 

 rays being absorbed by the varnish. The negative pole 

 of an electric machine was connected to this plate, the 

 positive pole being connected to the tin foil, and the light 

 of an electric arc allowed to fall on the under plate for a 

 few seconds. The plate of ebonite being removed 

 and powdered over with a mixture of sulphur and red 

 lead a yellow cross on a red background was 

 obtained of the same size as the one traced on the brass 

 plate. As the sulphur attaches itself to those parts of 

 the plate which are positively, and the red lead to those 

 which are negatively charged, it follows that the parts 

 of the lower plate which were not protected by the varnish 

 have lost some of their negative charge, which has been 

 carried on to the ebonite plate, and that this displace- 

 ment has followed the lines of force of the electric field 

 between the plates, which are in this case perpendicular 

 to the two plates. This conclusion is further strengthened 

 by observing that, if the electrified particles which escape 

 from the lower plate are prevented, by means of a screen, 

 from reaching the ebonite, a shadow of the screen is 

 obtained. 



The explanation that this convection is caused by the 

 molecules of gas which, after being in contact with the 

 body, become charged and are repelled, is hardly satis- 

 factory, and the experiments of MM. Lenard and Wolf 

 seem to show that it is particles of dust which carry the 

 charge, for they suspended an insulated plate of metal in 

 a box filled with air which had been carefully freed from 

 dust. A plate of quartz fixed in one side of this box 

 allowed the light from an electric arc to fall on the metal 

 plate, while a stream of some vapour could be introduced 

 through a side tube. Under these circumstances the 

 vapour was condensed on allowing the light to fall on the 

 plate if It was uncharged or negatively charged, while if 

 the plate was positively charged no condensation took 

 place. As it is known that a given space can become 

 supersaturated with vapour when no dust is present, but 

 that the introduction of the least trace of dust causes an 

 immediate condensation, it appears that when a body 

 either uncharged or negatively charged is illuminated it 

 gives off some dust, and that the loss of charge is due to 

 this dust. Further particulars of the work which has 

 been done in this subject are given in a paper by M. 

 Blondm in Electricitc, p. 313, 1893. W. W. 



AEOLITHIC DISCO VERIES IN BELGIUM. 

 'T^HE fact that in Belgium flint was in certain districts 

 -*■ largely worked durmg Neolithic times, for the manu- 

 facture of hatchets and other implements, has long been 

 well known. The mines in the chalk near Mons, from 

 which the rough blocks of flint were procured by the 

 ancient flint-workers, have frequently been described, and 

 bear a close analogy with the old workings at Grimes' 

 Graves, near Brandon, and with the pits near that place, 

 still being sunk by the flint-knappers of the present day. 

 The fields in the neighbourhood of Mons have their sur- 

 face strewn with roughly-chipped hatchets, and in other 

 districts the occurrence of worked flints has been not 

 unfrequently noted. In a memoir, recently published in 

 the Bulletin de la Souetc d'Anthropologie de Bruxelles 

 (Tome xi. 1892-93), M. G. Cumont has placed on 

 record his discovery of two important Neolithic stations 

 at Verrewinckel and Rhode-Saint-Gencse, neither of 

 which places is far from the main road from Brussels to 

 Charleroi, while both lie at but a short distance from the 

 field of Waterloo. The forest of Soignes extended in early 



NO. 1262, VOL. 49] 



times over the whole district, and though both stations 

 are on promontories of high land, there are or were, in 

 the neighbourhood of each, springs or ponds from which 

 to obtain a supply of water and, possibly, of fish. 



The principal of the two was that at Rhode-Saint- 

 Genese, whence, including flakes and scrapers, M. 

 Cumont has obtained no less than 3591 worked flints, a 

 few implements made of other kinds of stone being 

 reckoned among them ; while Verrewinckel is credited 

 with 815 specimens. Of all the forms a good summary 

 account is given, and characteristic examples are figured 

 in five plates. A detailed map of the district is also 

 given. That the manufacture was carried on at the 

 stations is proved by the presence of upwards of 240 

 nuclei from which flakes have been dislodged ; but few of 

 these appear to have rivalled in size those of specimens 

 near Mons. It is indeed suggested that the hatchets and 

 larger implements were rough-hewn at Spiennes, and 

 finished where they were found. That this was the case 

 is further shown by the fact that some twenty polissoirs 

 were collected by M. Cumont, who also regards the flint 

 which forms the material of the implements as having 

 been derived from Spiennes, dbourg, or the neighbour- 

 hood of Mons. Over a hundred arrow-heads figure in 

 the lists, and some of these, as shown in the plates, 

 exhibit skilful workmanship. A few quaternary or 

 palaeolithic implements from the same region have been' 

 described by M. Cumont in another paper. He is to 

 be congratulated on the rich harvest that he has reaped 

 by his labours, which have now extended over a period of 

 eight years. J. E. 



THE LATE SIR SAMUEL BAKER. 



NOTHING impresses more vividly upon one the 

 rapid unfolding of our knowledge of Africa than 

 the fact that the pioneers who forced the first paths into 

 the unknown interior have survived to see generation 

 after generation of younger men, who followed in their 

 footsteps, fall victims to the fatal fascination of that 

 continent. Burton, Grant, and Oswell, the companion of 

 Livingstone's earliest journeys, have died so recently that 

 we realise with a feeling of sorrowful surprise that the 

 last of the first great group of explorers has passed 

 away in the person of Sir Samuel White Baker, on 

 December 30, 1893. 



He was born in London in 1821, and after his school 

 education turned his attention to engineering, but his 

 professional work never took so thorough a hold upon his 

 mind as the love for travel and sport, which his private 

 means fortunately enabled him to gratify to his heart's 

 content. Baker first went to Ceylon for elephant shooting 

 in 1845, ^rid saw a great deal of the island in subsequent 

 years. Two books resulted from this experience — " The 

 Rifle and Hound in Ceylon," published in 1854, and 

 " Eight Years' Wanderings in Ceylon," in 1855. The 

 study which he made of the climate of the elevated part 

 of Ceylon led him to estabhsh a colony of English agri- 

 culturists, fully equipped with a stock of cattle and sheep, 

 at Nowera Eliya, over 6,000 feet above the sea, which is 

 now a noted health resort. On the death of his wife, in 

 i855,he went tothe Crimea, and carried out some railway 

 work subsequently on the Black Sea coast. In i860 he 

 married a Hungarian lady, who surviveshim, after beinghis 

 devoted companion through the trying years of .African ad- 

 ventures, and in the pleasanter wanderings of his later life. 



In 1861 he went to Egypt, resolved to carry on an ex- 

 tensive scheme of exploration at his own expense. With 

 this object he spent a year in Abyssinia, working out the 

 complete hydrography of the Atbara and its tributaries, 

 and then started from Khartum to follow up the White 

 Nile itself. In February, 1863, he met Speke and Grant 

 at Gondokoro, returning from their great journey to the 



