September 1, 1890.] 



KNOWLEDGE 



207 



The above are the three great types of the offensive 

 armature with which the skulls of existing Mammals are 

 provided, and they are all of them, as already observed, 

 found in the order of Hoofed Mammals, and nowhere else, 

 at the present day. If, however, we go back to the long- 

 distant Mesozoic epoch, or period, at which our chalk was 

 deposited at the bottom of the sea, we find that certain 

 herbivorous species of the gigantic reptiles known as 

 Dinosaurs (of which we hope to speak in a future article) 

 were provided with paired bony horn-cores on their skulls, 

 so exactly resembling those of our own Oxen that some of 

 them when found detached were actually described as be- 

 longing to an extinct Bison. In the later Tertiary beds of 

 Australia, we also find a huge tortoise with somewhat 

 similar horn-cores on its forehead ; and since these horn- 

 cores, both in this and the preceding instance, so closely 

 simulate in structure those of the Oxen, we may fairly 

 infer that they were similarly sheathed with true horns 

 during life. 



Thus we learn that in long past epochs not only was the 

 place of the larger herbivorous Mammals of the present 

 day taken by various forms of giant herbivorous reptiles, 

 but that those reptiles were actually armed with weapons 

 precisely similar to those of the Mammals of the present 

 day. So true is it that there is " nothing new under the 

 sun." 



OLD HINDU ALGEBRA. 



In India, at the time of Arya-Bhatta 1,700 years ago, 

 minus quantities were distinguished by a dot over the 

 coefficient, all unmarked quantities being held to be posi- 

 tive or plus. Multiplication was indicated by a dot 

 between the factors ; and division by placing the divisor 

 under the dividend, much in our own way ; but squares, 

 cubes, unknowns, &c., were indicated by initial letters of 

 the words expressing the ideas, thus — 



r for raiya =: square. 

 ///( for ijhund = density, cube. 

 (ju for (iiind = multiplication. 

 ril for riipa = form, the definite quantity. 

 &c. &c. &c. 



Coefficients were placed nftcr the literal symbols ; and 

 an unknown quantity was generally expressed by y, the 

 initial of yih-i(t-ti1ritt, " this-nnieh-tliat-much," or " any- 

 nuicli." Other unknowns to any number were expressed 

 by initials of the names of colours. An instance will 

 sjiow the use of these .symbols ; thus for — 



12 j'Hl «"-3 a-- 

 the ancient Hindus wrote — 



4 X? 



.'/'■ 1-^ mil' i III- •* • ■'■' J 



Their method of wiiting an equation was more awkward 

 than ours, and while everything else is so obvious the 

 reason for it is not apparent ; thus for — 



they would write- 



12 .r-- 8 x' = 14 



yr 12 y<ih 8 rn 

 2/c yijh (•// 14 



The second line is given as the equivalent of the first 

 line, ciphers being supplied where required. 



FliEIlKKlr PlNCOTT. 



WHY IS THE SEA SALT? 



By W. Mattieu Williams. 

 (Continued from p. 179.) 



IN my last I described the variations in the degree of 

 salinity of the ocean, and the causes of such varia- 

 tion, and concluded by reference to the apparent 

 paradox that the river-flows which are reducing 

 immediate local salinity are the main sources of the 

 general salinity. 



The paradox vanishes when we consider the fact that 

 the ocean simply occupies the lower valleys of the earth, 

 and that the dry land consists of its mountain summits and 

 their upper slopes only. This portion of the earth slopes 

 towards the main or oceanic valley, and thus all the drainage 

 and washings of the exposed land surface proceed to the 

 ocean. The inisoluble portion of these washings are de- 

 posited as ocean-bed strata, the soluble portions remain in 

 solution in quantity dependent on their solubility. Kiver- 

 water or spring-water, as we all know, is more or less 

 " hard," but the rain-w-ater, from which all these hard 

 waters are derived, is " soft." 



The hardness of the hard water is due to saline impuri- 

 ties held in solution ; the softness of soft water, to the 

 absence of these. The ocean is being continually distOled 

 by solar heat, and the distilled water, thus lifted into the 

 atmosphere and falling on the earth as rain, is pure, soft, 

 or free from saltness. Therefore the saline materials 

 which give hardness to the river-water are derived from 

 the land, and must be left behind in the sea. 



It is true that the quantity of such saline matter dis- 

 solved in the water that enters the sea at the mouths of 

 rivers is very small, but "many a mikle maks a mukle," 

 and this everlasting supply of small contributions that has 

 been going on as long as the surface of the earth has 

 consisted of land and water, is amply sufficient to accoimt 

 for the i/tituititii of salt in the ocean. 



If this explanation is correct, a confirmation should be 

 found in all inland bodies of water, all lakes and seas that 

 have no outlet. The great Canadian lakes, the lakes of 

 Constance, Geneva, &c. are merely outspread rivers — 

 streams that pour into a deep, wide valley at one end and 

 run out of it at the other. Thus, the Lake of Geneva is 

 but an outspread of the Ehone, the Lake of Constance an 

 outspread of the Rhine. But there are other lakes with 

 no such lower outlet — lakes that only retain their normal 

 level (as the ocean does) by evaporating as much as they 

 receive from rain and the river or ri\ers that supply them. 

 As they thus receive hard or slightly saline water and give 

 olf only soft or pure water, they should represent the ocean 

 in respect to salinity. This is the case. Many are more 

 strongly saline than the sea itself. This is especially the 

 case in hot countries, where the amount of evaporation is 

 great. 



The Dead Sea is a popular example of this. It occupies 

 a deep trough-like valley, and receives at one end the 

 famous river .lordan, and at the other, and from its sides, 

 a multitude of mmor rivers and rivulets. The whole of 

 this surplus supply of water is removed by solar distilla- 

 tion ; the amount of such distillation varying — other 

 conditions being equal — with its surface. As the land is 

 sloping on all sides, the height of the lake cannot increase 

 without a corresponding increase of surface and conse- 

 quent increase of evaporation. Thus an automatic regu- 

 lation is perpetually maintained. If the river supplies 

 diminish, the area of surface of the lake and the amount 

 of evaporation diminish, and rice rrrsd. The excessive 

 briny saltness of this lake is well known and easily 

 accounted for by the above explanation. 



