267 



SCIENTIFIC SIDE-LIGHTS 



*orce 

 ^orests 



and so excessively finely divided was it 

 that it penetrated into all drawers, boxes, 

 and the most closely fastened receptacles, 

 filling them completely. JUDD Volcanoes, 

 ch. 4, p. 68. (A., 1899.) 



1302. FORCES UNSEEN IN THE AIR 

 WE BREATHE Mountains Precipitate Invis- 

 ible Vapor. The atmospheric change [after 

 crossing the Simplon to the Italian lakes] 

 was wonderful ; and still the clear air which 

 w r e enjoyed below was the selfsame air that 

 heaped clouds and snow upon the moun- 

 tains. It came across the heated plains of 

 Lombardy charged with moisture, but the 

 moisture was in the transparent condition 

 of true vapor, and hence invisible. Tilted 

 by the mountains, the air rose, and as it 

 expanded it became chilled, and as it be- 

 came chilled it discharged its vapor as vis- 

 ible cloud, the globules of which swelled 

 by coalescence into raindrops on the moun- 

 tain flanks, or were frozen to snow upon the 

 mountain. TYNDALL Hours of Exercise in 

 the Alps, ch. 22, p. 261. (A., 1898.) 



1303. FORCES, UNSEEN, POWER OF 

 Bonds of Wire or Steel to Equal Sun's 

 Attraction. As for the attraction between 

 the sun and earth, it amounts to thirty-six 

 hundred quadrillions of tons: in figures, 

 36 followed by seventeen ciphers. On this 

 point we borrow an impressive illustration 

 from a careful calculation by Mr. C. B. 

 Warring. We may imagine gravitation to 

 cease, and to be replaced by a material bond 

 of some sort, holding the earth to the sun 

 and keeping her in her orbit. If now we 

 suppose this connection to consist of a web 

 of steel wires, each as large as the heaviest 

 telegraph-wires used, then to replace the 

 sun's attraction these wires would have to 

 cover the whole sunward hemisphere of our 

 globe about as thickly as blades of grass 

 upon a lawn. It would require nine to each 

 square inch. Putting it a little differently, 

 the attraction between the sun and earth is 



equal to the breaking strain of a steel rod 

 about 3,000 miles in diameter. YOUNG The 

 Sun, ch. 1, p. 41. (A., 1898.) 



1304. FORCES, VITAL AND MATE- 

 RIAL Terms Ill-understood. What is a vi- 

 tal force? It is something which we can- 

 not see, but of whose existence we are as 

 certain as we are of its visible effects nay, 

 which our reason tells us precedes and is 

 superior to these. We often speak of ma- 

 terial forces as if we could identify any 

 kind of force with matter. But this is only 

 one of the many ambiguities of language. 

 All that we mean by a material force is a 

 force which acts upon matter, and produces 

 in matter its own appropriate effects. We 

 must go a step further, therefore, and ask 

 ourselves, what is force? What is our con- 

 ception of it? What idea can we form, 

 for example, of the real nature of that force 

 the measure of whose operation has been so 

 exactly ascertained the force of gravita- 

 tion ? It is invisible imponderable all our 



words for it are but circumlocutions to ex- 

 press its phenomena or effects. ARGYLL 

 Reign of Law, ch. 2, p. 71. (Burt.) 



1 3O5. FORCES WORKING IN UNISON 



Light, Heat, and Electricity Inseparably 

 Connected with Motion and Life. Light, 

 and radiating heat, which is inseparable 

 from it, constitute a main cause of mo- 

 tion and organic life, both in the non-lumi- 

 nous celestial bodies and on the surface of 

 our planet. Even far from its surface, in 

 the interior of the earth's crust, penetrating 

 heat calls forth electromagnetic currents, 

 which exert their exciting influence on the 

 combinations and decompositions of mat- 

 ter on all formative agencies in the min- 

 eral kingdom on the disturbance of the 

 equilibrium of the atmosphere and on the 

 functions of vegetable and animal organ- 

 isms. If electricity moving in currents de- 

 velops magnetic forces, and if, in accordance 

 with an early hypothesis of Sir William 

 Herschel, the sun itself is in the condition 

 of " a perpetual northern light " ( I should 

 rather say of an electromagnetic storm ) , 

 we should seem warranted in concluding 

 that solar light, transmitted in the regions 

 of space by vibrations of ether, may be ac- 

 companied by electromagnetic currents. 

 HUMBOLDT Cosmos, vol. iii, p. 34. (H., 

 1897.) 



1306. FOREST, PRIMEVAL Brazil 

 Terra del Fuego Silent Message of the God 

 of Nature. Among the scenes which are 

 deeply impressed on my mind, none exceed 

 in sublimity the primeval forests undefaced 

 by the hand of man; whether those of Bra- 

 zil, where the powers of life are predomi- 

 nant, or those of Terra del Fuego, where 

 death and decay prevail. Both are temples 

 filled with the varied productions of the God 

 of Nature no one can stand in these soli- 

 tudes unmoved, and not feel that there is 

 more in man than the mere breath of his 

 body. DARWIN Naturalist's Voyage around 

 the World, ch. 21, p. 503. (A., 1898.) 



1307. FORESTS BURIED UNDER 



DRIFT The Elephant, Rhinoceros, and Hip- 

 popotamus Once Ranged in England. At 

 one of the most charming spots on the coast 

 of Norfolk, Cromer, you will see the boul- 

 der-clay forming a vast mass, which lies 

 upon the chalk, and must consequently have 

 come into existence after it. I have spoken 

 of the boulder-clay and drift as resting upon 

 the chalk. That is not strictly true. In- 

 terposed between the chalk and the drift 

 is a layer containing vegetable matter. But 

 that layer tells a wonderful history. It is 

 full of stumps of trees standing as they 

 grew. Fir-trees are there with their cones, 

 and hazel-bushes with their nuts; there 

 stand the stools of oak- and yew-trees, 

 beeches and alders. Hence this stratum is 

 appropriately called the " forest-bed." 



It is obvious that the chalk must have 

 been upheaved and converted into dry land 

 before the timber trees could grow upon it. 



