438 



SCIENCE, 



[Vol. IV., No. 92. 



springs in a straight line. As for the ether itself, it 

 is to be considered as a substance which may not be 

 an elastic solid, but which, so far as the luminiferous 

 vibrations are concerned, moves as if it were an elas- 

 tic solid. The lecturer carried on the mathematical 

 discussion of these two dynamical problems — the 

 propagation of waves in an elastic solid, and the mo- 

 tion of a system [of spring-connected particles in a 

 straight line — side by side, usually devoting the first 

 half of a lecture to one problem, and the remainder 

 to the other. 



It is impossible here to give any specific account of 

 the contents of the lectures; it may be stated, how- 

 ever, that many of the cardinal phenomena of light 

 were shown to be explicable by the hypothesis 

 sketched above, but that the phenomenon of double 

 refraction presented apparently insuperable difficul- 

 ties, as it has done in all previous attempts to explain 

 it. By proper suppositions regarding the elasticity 

 of the springs (in the mechanical 'model ' of the phe- 

 nomenon given above) double refraction would indeed 

 be produced; but its law would be widely different 

 from that actually observed. 



The lecturer was conversational in his manner, 

 made almost no use of notes, and was full of enthu- 

 siasm for his subject. The audience was composed 

 of professors of physics from eastern and western 

 colleges, scientific men from Washington, and stu- 

 dents and instructors of the Johns Hopkins univer- 

 sity. The lectures, while not condensed in form, 

 presupposed thorough familiarity with the physical 

 and mathematical theories involved. A verbatim 

 report of them, from stenographic notes, wilLbe issued 

 in a limited edition, by the use of the papyrograph 

 process. At the close of the course, Sir William 

 Thomson was presented by the class with one of Row- 

 land's concave gratings, as a memento of their con- 

 nection with him. 



tool to the primitive man is evident from their wide 

 distribution. They have been found in France, in 

 the Crimea, in India, in America (both North and 

 South), and now we have them from Africa. The 

 strata in which they have been found are of great 

 antiquity. 



The archeology of the North-African coast has 

 especial claims to attention, as from there, apparently, 

 a very ancient migration advanced northward, pass- 

 ing in one direction through Spain, and in another 

 by way of Malta, Sicily, and Italy. This migration 

 was apparently contemporary with the appearance of 

 the Elephas africanus in Europe. Another point of 

 interest, connected with North- African archeology, is 

 found in the fact that the only locality in the old 

 world where animal or effigy mounds have been re- 

 ported is in Algiers, near the forest of Tenrit-el-Sad, 

 south of Miliana. As these peculiar structures are 

 so frequent in the Mississippi valley, the coincidence 

 is worth noting. 



Prof. A. Heilprin contended, that while on the 

 hypothesis of evolution, no objection could be raised 

 to an assumption which made an animal intermediate 

 between man and the anthropoid apes sufficiently 

 intelligent to understand the full value and manu- 

 facture of stone implements, such as were exhibited, 

 yet, as a matter of fact, paleontological evidence had 

 thus far failed to prove that any such use or manu- 

 facture had been made of them, as was claimed. 

 Indeed, no evidence was forthcoming to show that 

 the implements were not the work of man himself, 

 despite the fact that no traces of human remains 

 have been found associated with the fragments. The 

 assumption that the advent of man dates only to a 

 given period of the so-called 'stone age' was con- 

 sidered to be purely gratuitous, and to rest solely on 

 negative evidence. Many archeologists concur in 

 the belief that man's remains may yet be found in 

 deposits of a strictly tertiary age. 



NORTH-AFRICAN ARCHEOLOGY. 



At a meeting of the Academy of natural sciences of 

 Philadelphia, Sept. 25, Dr. Daniel G. Brinton called 

 attention to a collection of flint-chips collected at the 

 station of Ras-et-Oued, near Biban, on the south- 

 eastern coast of Tunis, and presented to the academy 

 by the Marquis de Nadaillac. The specimens con- 

 sisted of flint-chips, arrow-points, and a serai-lunar 

 shaped implement of small size, which resembles the 

 ' stemmed scrapers ' found in America. This form 

 was obtained from lower levels below the surface, 

 and is characteristic in France of the later produc- 

 tions of the stone age, especially of that epoch called 

 by the French archeologists ' the epoch of Roben- 

 hausen,' from the locality of that name in Switzer- 

 land. Chronologically this is regarded as the first 

 epoch of the appearance of man on the globe, the 

 previous implement-using animals being probably 

 anthropoids. These made use of stone only, not 

 having learned the dressing of bone or horn. This 

 view adds to the interest of the query as to the pur- 

 pose of these scrapers. That they were an important 



THE LIMITATIONS OF SUBMARINE 

 TELEGRAPHY. 1 



The weight of the conductors, says Henry Vivarez 

 in La lumiere electrique, plays an important part in 

 submarine telegraphy, not merely as a heavy item in 

 the outlay, but as one of the principal factors in lay- 

 ing down the lines, and in taking them up in case of 

 damage. When the conductor is being raised, the 

 grappling-irons which lift it have to resist not merely 

 the vertical component of the weight of the cable, 

 but also the considerable effects resulting from fric- 

 tion against the water. It thus frequently happens, 

 when working at great depths, that the conductor may 

 be exposed to a strain greater than it is able to bear, 

 and we are forced to have recourse to stratagems to 

 bring it to the surface. These artifices consist in the 

 use of two or more ships in raising, which is done as 

 shown in figs. 2 and 3, or, in the most simple cases, 



1 Reproduced in abridged form from the Electrical review, 

 and the cuts from La lumiere electrique. 



