657 



SCIENTIFIC SIDE-LIGHTS 



Storms 

 Strength 



side, instead of being affected like the young 

 in other mammals, and sticking closer to 

 its mother, acts in a contrary way, and runs 

 from her. HUDSON Naturalist in La Plata, 

 ch. 6, p. 110. (C. & H., 1895.) 



3247. STREAM OF LAVA HARD- 

 ENED INTO STONE A Frozen Cataract- 

 Eruption of Etna. The lava [flowing from 

 Etna in 1669], after overflowing fourteen 

 towns and villages, some having a popula- 

 tion of between three and four thousand 

 inhabitants, arrived at length at the walls 

 of Catania. These had been purposely raised 

 to protect the city, but the burning flood 

 accumulated till it rose to the top of the 

 rampart, which was sixty feet in height, 

 and then it fell in a fiery cascade and 

 overwhelmed part of the city. The wall, 

 however, was not thrown down, but was dis- 

 covered long afterwards by excavations made 

 in the rock by the Prince of Biscari, so that 

 the traveler may now see the solid lava curl- 

 ing over the top of the rampart as if still 

 in the very act of falling. LYELL Principles 

 of Geology, bk. ii, ch. 25, p. 400. (A., 1854.) 



3248. 



Entrapped Hill Melted Down. As another 

 illustration of the solidity of the walls of 

 an advancing lava-stream, I may mention 

 an adventure related by Recupero, who, in 

 1766, had ascended a small hill formed of an- 

 cient volcanic matter, to behold the slow and 

 gradual approach of a fiery current, two 

 miles and a half broad, when suddenly two 

 small threads of liquid matter issuing from 

 a crevice detached themselves from the main 

 stream and ran rapidly towards the hill. 

 He and his guide had just time to es- 

 cape, when they saw the hill, which was 

 fifty feet in height, surrounded, and in a 

 quarter of an hour melted down into the 

 burning mass, so as to flow on with it. 

 LYELL Principles of Geology, bk. ii, ch. 25, 

 p. 401. (A., 1854.) 



3249. STRENGTH DEVELOPED 

 BY RESISTANCE Growing Plants Made 

 Stronger 6t/ Stress and Strain. Many 

 commonplace facts indicate that the me- 

 chanical strains to which upright growing 

 plants are exposed themselves cause increase 

 of the dense deposits by which such plants 

 are enabled to resist such strains. There 

 is the fact that the massiveness of a tree- 

 trunk varies according to the stress habitu- 

 ally put upon it. ... A tree trained 

 against a wall has a less bulky stem than a 

 tree of the same kind growing unsupported ; 

 and between the long, weak branches of the 

 one and the stiff ones of the other there 

 are decided contrasts. Garden plants, which 

 when held up by tying them to sticks have 

 weaker stems than when they are unpropped, 

 and sink down if their props are taken 

 away. . . . Trees growing on inclined 

 rocky surfaces send into crevices that afford 

 little moisture or nutriment roots which 



nevertheless become thick where they are so 

 directed as to bear great strains. SPENCER 

 Biology, pt. iv, ch. 4, p. 275. (A., 1900.) 



3250. 



Strongest Corals 



Grow in Hardest Surf Vital Energies Con- 

 quer Mechanical Power. It has been a ques- 

 tion with some naturalists which part of a 

 reef is most favorable to the growth of coral. 

 The great mounds of living porites and of 

 millepora round Keeling atoll occur exclu- 

 sively on the extreme verge of the reef, which 

 is washed by a constant succession of break- 

 ers; and living coral nowhere else forms solid 

 masses. At the Marshall Islands the larger 

 kinds of coral, . . . "which form rocks 

 measuring several fathoms in thickness,'* 

 prefer . . . the most violent surf. I 

 have stated that the outer margin of the 

 Maldiva atolls consists of living corals ( some 

 of which, if not all, are of the same species 

 with those at Keeling atoll), and here the 

 surf is so tremendous that even large ships 

 have been thrown, by a single heave of the 

 sea, high and dry on the reef, all on board 

 thus escaping with their lives. . . . The 

 vital energies of the corals conquer the me- 

 chanical power of the waves; and the large 

 fragments of reef torn up by every storm 

 are replaced by the slow but steady growth 

 of the innumerable polypifers which form 

 the living zone on its outer edge. ... It 

 is certain that the strongest and most mas- 

 sive corals flourish where most exposed. 

 DARWIN Coral Reefs, ch. 4, p. 85. (A., 1900.) 



3251. STRENGTH, MAN'S, PROPOR- 

 TIONED TO EARTHLY NEEDS Weakness 

 of Gravity on the Moon Cyclopean Amphi- 

 theaters and Volcanoes. Gravity at the sur- 

 face of the moon is weaker than with us; 

 if we represent by 1,000 the force which 

 causes objects to adhere to the terrestrial 

 globe, that on the moon would be represent- 

 ed by 164. Hence, objects weigh there six 

 times less than here; they are attracted 

 six times less strongly. A stone weighing 

 one pound, if transported to the moon, would 

 not weigh more than 3 ounces. A man 

 weighing 11 stone on our planet would not 

 weigh there more than 26 pounds. If we 

 imagine a man transported to our satellite, 

 if we suppose, moreover, that his muscular 

 powers would remain the same in this new 

 abode, he would be able to raise weights 

 five to six times heavier than on the earth, 

 and his own body itself would seem to be 

 five or six times lighter. The least mus- 

 cular effort would enable him to spring 

 to enormous heights or to run with the 

 speed of a locomotive. [It must be observed] 

 what a considerable part this weakness of 

 gravity has played in the topographical or- 

 ganization of the lunar world, by permitting 

 the volcanoes to pile up giant mountains on 

 Cyclopean amphitheaters, and with a power- 

 ful hand to toss Alps upon Pyrenees. 

 FLAMMARION Popular Astronomy, bk. ii, 

 ch. 3, p. 110. (A.) 



