58 



NATURE 



[Nov. 20, 1879 



found the first land mollusca on the Tchuktch Peninsula. 

 Nordenskjold considers it probable that on the southern 

 part of this peninsula there was in former times a little 

 inland ice. On July 31 the Vega was anchored at St. 

 Lawrence Island. Drift ice was seen for the last time. 

 The quantity of ice carried by the Polar current through 

 Behring's Straits is very inconsiderable, and it has 

 evidently been for the most part formed along the coast. 

 Not a single iceberg was visible, the whole of the ice 

 seen being level and rotten "year's ice." St. Lawrence 

 Island is inhabited by Eskimo, who having frequent inter- 

 course with the Tchuktches, have adopted some of their 

 words. The prevailing rock is granite, weathering readily, 

 and thus giving origin to a very fruitful soil. Vegetation 

 was exceedingly luxuriant, and rich collections of land and 

 marine animals, lichens, and alga; were made. 



The Vega next anchored off Behring Island on August 

 14. This island belongs to Russia, but the American 

 Alaska Company has acquired the right of hunting, and 

 maintains a station where skins, principally those of the 

 Of aria ursiiia, are purchased. Between 50,000 and 

 100,000 of these animals are killed yearly on this and the 

 neighbouring Copper Island. They yield the brown 

 " sealskin " so much in fashion in recent years. Behring's 

 Island is supposed to have been visited first by Behring, 

 who, after being shipwrecked, died there in 1741, survived, 

 however, by many of his companions, among others, by 

 the talented naturalist Steller, who described the natural 

 history of the island in a masterpiece that has seldom 

 been surpassed. Since Steller's time great changes have 

 taken place. The Canis lagopus then occurred in in- 

 credible numbers. Now they are so uncommon that not 

 one was seen, and those that remain are not dark blue, 

 but white, the skins being of little value. On the neigh- 

 bouring Copper Island dark blue foxes are still found in 

 considerable abundance. In 1741-4.2 Stellar and his com- 

 panions killed here about 700 sea-otters. This animal, 

 famous for its precious fur, is now quite extinct on 

 Behring's Island. Of the sea-lion {Otaria stelleri), formerly 

 abundant, only single specimens are to be found along 

 with the sea-bear {Otaria itrsina) on the rocky shores of 

 the island, and the great sea-cow, the most remarkable of 

 all the mammals formerly belonging to Behring's Island, 

 is now completely extinct. Steller's sea-cow (Rkytina 

 stelleri) was of a brownish colour, covered with hair which 

 grew on a hide resembling the bark on an old oak. Its 

 length, according to Steller, was sometimes as much as 

 thirty-five feet and its weight nearly 50,000 lb. The female 

 yielded abundance of milk, which, along with the flesh, 

 resembled, and were even, according to Stellar, superior 

 to those of the cow. The sea-cow fed on the abundant 

 alga: along the coast in great herds. According to 

 Midden Jorf, the last sea-cow was killed in 1768. Nor- 

 denskjold, however, found a " Creole" of mixed Russian 

 and Aleutian blood, whose father had come to the island 

 in 1777, and remembered the killing of sea-cows while 

 they fed on seaweed at low water for the first two or three 

 years (1779 or '78o) after his arrival. Nordenskjold 

 also found two men who had seen, about twenty-five 

 years ago, a large animal corresponding to Steller's sea- 

 cow. He also obtained two complete skulls of the animal 

 and a quantity of bones sufficient to fill twenty-one large 

 boxes and barrels. The sea-bear (Otaria ursina) is the 

 only large animal that exists on the island in about as 

 large numbers as in Steller's time. It is "preserved" 

 by the Alaska Company, only a limited number being 

 killed yearly. 



The vegetation on Behring's Island was found to be 

 exceedingly luxuriant, and the sea in its neighbourhood 

 one of the richest in alg;e in the world. Forests of alga;, 

 sixty to a hundred feet high, grew in favourable situa- 

 tions, rendering dredging exceedingly difficult. Some of 

 the alga: are used by the natives as food. 



The small streams swarmed with a number of different 



kinds of fish, among them a species of Coregonus, a little 

 Sahno fario, a middle-sized salmon with nearly white 

 flesh and a purple skin, and another of the same length, 

 but very thick, and with a hump on its back. Other 

 species of salmon with deep red flesh are found in the 

 larger rivers. Leaving Behring's Island on August 19, the 

 Vega reached Yokohama on September 2 in good order 

 and with every man on board in excellent health. There 

 had not been a trace of scurvy during the whole voyage. 



GALILEO AND THE APPLICATION OF 

 MATHEMATICS TO PHYSICS' 



II. 



IN dealing with the falling body I had to ask you to think 

 what is the speed at any moment of a body which 

 is changing its speed every moment, every half moment, 

 every hundredth part of a moment or what we call con- 

 tinuously. It is easy to see that it has some speed at 

 every point, and that the speed at every point is quite 

 definite. I indicated a way in which we could fix this 

 approximately, by taking the average speed over short 

 intervals. A similar question is raised in considering the 

 path of the projectile. Its direction changes from point 

 to point. The bullet is shot towards the east, and, for 

 the sake of picturing its path, I imagine the lines vertically 

 upward to be called northwards, as on a vertical map. 

 At first the particle starts off, let me say, in a direction 

 N.N.E. When it has reached the top of its path it is 

 going horizontally — due east — when it has got back to the 

 level the Northing has been turned into Southing, and it 

 is going S.S.E. In its upward motion it changes con- 

 tinuously from N.N.E. to E. At a certain position it is 

 half a point more to the east and less to the north ; 

 further on, a point more ; further on again, the Northing 

 has disappeared. The path has curved away ; it is 

 curving away at every point of it. A particle moving at 

 a uniform rate in a circle changes its direction ; but at 

 every point the amount of curvature or immediate bend- 

 ing away from the direction in which the particle moves 

 at any moment is the same. In a small circle the curve 

 bends away faster than in a larger one from the line which 

 represents the direction of motion at any point, but in 

 each separate circle the measure of bending must at 

 every point be the same. How will it be in a different 

 kind of curve, such as an ellipse, or the path of a pro- 

 jectile, a parabola ? As the speed of falling changes from 

 moment to moment continuously, the curvature changes 

 from moment to moment. ■ 



In solving the problems of falling bodies and of pro- 

 jectiles, Galileo was essentially applying the principles of 

 the Differential or Fluxional or Indivisible Calculus. If 

 pure mathematics had attracted him as strongly as its 

 application to physics, he wou'd have thought these 

 problems out, and would have founded the Fluxional 

 Calculus, which is the glory of Newton and of Leibnitz. 

 No doubt the world saw more in his great astronomical 

 discoveries ; in the telescope, which brought the moon 

 thirty times nearer, and showed its mountains and the 

 jagged edges of its gibbous side ; in the discovery 

 that Venus waxes and wanes with phases like the moon ; 

 in the four satellites of Jupiter, the famous Medicean 

 stars, which showed the most restless activity of revolu- 

 tion round their central orb — an activity unprecedented 

 in celestial bodies and discomposing to the Peripatetics, 

 whose stately order of the heavens could not tolerate 

 stars which behaved like sky rockets— of the curious 

 double satellite of Saturn, which sometimes was even more 

 bewildering, and went out altogether. It was the Ring, 

 and Galileo gave what we now recognize as a very fan- 

 picture of it. No wonder that the man who first made the 

 1 An Introductory Lecture, by William Jack. M.A., LL.D., F.R.S.E., 

 Professor of Mathematics in the University of Glasgow, formerly bellow of 

 St. Peter's College, Cambridge. Continued from p. 43. 



