Progress 

 Protection 



SCIENTIFIC SIDE-LIGHTS 



560 



springs, upon a railway which is in excellent 

 order, the movement is almost imperceptible 

 to us, and the rate of speed may be increased 

 indefinitely without making itself apparent 

 to our senses. The smallest impediment to 

 the evenness of the movement such as that 

 produced by a small object placed upon the 

 rails at once makes itself felt by a violent 

 jar and vibration. How perfectly insensible 

 we may be of the grandest and most rapid 

 movements is taught us by the facts demon- 

 strated by the astronomer. By the earth's 

 daily rotation we are borne along at a rate 

 which in some places amounts to over 1,000 

 miles an hour, and by its annual revolution 

 we are every hour transported through a 

 distance of 70,000 miles; yet concerning the 

 fact and direction of these movements we 

 are wholly unconscious. JUDD Volcanoes, 

 ch. 10, p. 285. (A., 1899.) 



2761. PROOF, FIRST, OF DEEP-SEA 

 FAUNA Commercial Industry Aids Science. 

 The first direct proof of the existence of 

 an invertebrate fauna in deep seas was 

 found by the expedition that was sent 

 to repair the submarine cable of the Medi- 

 terranean Telegraph Company. The cable 

 had broken in deep water, and a ship was 

 sent out to examine and repair the damage. 

 When the broken cable was brought on deck 

 it bore several forms of animal life that 

 must have become attached to it and lived 

 at the bottom of the sea in water extending 

 down to a depth of 1,200 fathoms. Among 

 other forms a caryophyllia was found at- 

 tached to the cable at 1,100 fathoms, an oys- 

 ter (Ostrea cochlear), two species of pec- 

 ten, two gasteropods, and several worms. 

 HICKSON Fauna of the Deep Sea, ch. 1, p. 

 7. (A., 1894.) 



2762. PROOFS FROM THE VAST AND 

 THE MINUTE UNITE Gases Imprisoned in 

 the Fluid Rock of Volcanoes. That the 

 molten materials which issue from volcanic 

 vents have absorbed enormous quantities 

 of steam and other gases we have the most 

 undisputable evidence. The volume of such 

 gases given off during volcanic outbursts, 

 and while the lava-streams are flowing and 

 consolidating, is enormous, and can only be 

 accounted for by supposing that the masses 

 of fluid rock have absorbed many times their 

 volume of the gases. But we have another 

 not less convincing proof of the same fact 

 in the circumstance that volcanic materials 

 which have consolidated under great pres- 

 sure such as granites, gabbros, porphyries, 

 etc. exhibit in their crystals innumerable 

 cavities containing similar gases in a lique- 

 fied state. 



It is to the violent escape of these gases 

 from the molten rock-masses, as the pressure 

 upon them is relieved, that nearly all the 

 active phenomena of volcanoes must be re- 

 ferred. -Juno Volcanoes, ch. 12, p. 357. (A., 

 1899.) 



2763. PROPAGATION, RECTILINEAR, 

 OF LIGHT Crossing of Rays with Inversion 



of Image Overlapping Images. The fol- 

 lowing instructive experiment depends on 

 the rectilinear propagation of light. Make 

 a small hole in a closed window-shutter, 

 before which stands a house or a tree, and 

 place within the darkened room a white 

 screen at some distance from the orifice. 

 Every straight ray proceeding from the 

 house or tree stamps its color upon the 

 screen, and the sum of all the rays will, 

 therefore, be an image of the object. But,, 

 as the rays cross each other at the orifice,, 

 the image is inverted. At present we may 

 illustrate and expand the subject thus: 

 In front of our camera is a large opening 

 from which the lens has been re- 

 moved, and which is closed at present by a, 

 sheet of tin-foil. Pricking by means of a 

 common sewing-needle a small aperture in 

 the tin- foil, an inverted image of the car- 

 bon-points starts forth upon the screen. A 

 dozen apertures will give a dozen images, a 

 hundred a hundred, a thousand a thousand. 

 But, as the apertures come closer to each 

 other, that is to say, as the tin-foil between 

 the apertures vanishes, the images overlap 

 more and more. Removing the tin-foil al- 

 together, the screen becomes uniformly il- 

 luminated. Hence the light upon the screen 

 may be regarded as the overlapping of in- 

 numerable images of the carbon-points. In 

 like manner the light upon every white wall 

 on a cloudless day may be regarded as pro- 

 duced by the superposition of innumerable 

 images of the sun. TYNDALL Lectures on 

 Light, lect. 1, p. 9. (A., 1898.) 



2764. PROPERTIES OF MATTER 

 TREATED AS CAUSES The physicist who 

 deduces from the activities of different forms 

 of matter certain " properties " which he 

 attributes to them, and then uses these very 

 " properties " to account for those activi- 

 ties, is obviously reasoning in a circle. 

 CARPENTER Nature and Man, lect. 15, p. 411. 

 (A., 1889.) 



2765. PROPHECY IN SCIENCE Spec- 

 tral Lines Foreseeing Discovery of ~New 

 Planet God Communicating with Rational 

 Creatures. If the possibility of God com- 

 municating with his rational creatures be 

 conceded, then the objections taken to 

 prophecy lose all value. If anything known 

 to God and unknown to man can be revealed, 

 things past and future may be revealed as 

 well as things present. Science abounds in 

 prophecy. All through the geological his- 

 tory there have been prophetic types, mute 

 witnesses to coming facts. Minute disturb- 

 ances of heavenly bodies, altogether inap- 

 preciable by the ordinary observer, enable 

 the astronomer to predict the discovery of 

 new planets. A line in a spectrum, without 

 significance to the uninitiated, foretells a 

 new element. The merest fragment, suf- 

 ficient only for microscopic examination, 

 enables the paleontologist to describe to in- 

 credulous auditors some organism altogether 

 unknown in its entire structures. What 



