339 



SCIENTIFIC SIDE-LIGHTS 



Infinity 

 Influence 



are of all others the most familiar. Both 

 the great conceptions of space and time are, 

 in their very nature, infinite. We cannot 

 conceive of either of these as subject to 

 limitation. We cannot conceive of a mo- 

 ment after which there shall be no more 

 time, nor of a boundary beyond which there 

 is no more space. This means that we can- 

 not but think of space as infinite and of 

 time as everlasting. ARGYLL Unity of Na- 

 ture, ch. 4, p. 79. (Burt.) 



166O. INFIRMITY UNCONSCIOUS 



Color-blindness Only Discovered by Compari- 

 son. It is an interesting fact in reference 

 to the dependence of at least one class of 

 our knowledge on sensation, that many 

 persons are born with defective vision and 

 yet remain for years of their lives without 

 being conscious of the deficiency. We know 

 a gentleman who had probably been always 

 near-sighted, but who did not discover the 

 peculiarity of his vision until the age of 

 twenty-five, when it was accidentally made 

 known by looking at a distant object 

 through a concave lens. Many persons 

 whose eyes are sound and capable of exerci- 

 sing the most delicate functions, are perma- 

 nently unable to distinguish certain colors. 

 And the number of such persons is much 

 more considerable than we would be led to 

 imagine from the little attention this defect 

 of vision has excited. It is often unknown 

 to the individual himself, and indeed only 

 becomes revealed by comparing his powers 

 of discriminating different colors with those 

 of other persons. HENRY Color-Blindness 

 (Scientific Writings, vol. i, p. 233). (Sm. 

 Inst., 1886.) 



1661. 



Experience of a 



Child with Color-blindness. An account is 

 given ... of a shoemaker, in Cumber- 

 land, who could distinguish in different col- 

 ors only a greater or less intensity of light, 

 calling all bright tints white and all dull 

 ones black. His peculiarity of vision was 

 unknown to him until one day, while a boy, 

 playing in the street, he found a stocking, 

 and for the first time was struck with the 

 fact that it was called by his companions 

 red, whereas to his mind it was capable of 

 no farther description than that designated 

 by the word " stocking " ; he was thus led 

 to conclude that there was something else 

 besides the form and position in the leaves 

 and fruit of a cherry-tree, perceived by his 

 playmates, but not seen by himself. HENRY 

 Color-Blindness (Scientific Writings, vol. i, 

 p. 235). (Sm. Inst., 1886.) 



1662. INFLUENCE EXERTED IN 

 VAIN Air Unwarmed by Burning Solar Rays. 

 On a sunny day you may see the summits 

 of the high Alps glistening with the water 

 of liquefaction. The air above and around 

 the mountains may at the same time be 

 many degrees below the freezing-point in 

 temperature. . . . Solar beams power- 

 ful enough to fuse the snows and blister the 

 human skin, nay, it might be added, power- 



ful enough, when concentrated, to burn up 

 the human body itself, may pass through the 

 air, and still leave it at an icy temperature. 

 TYNDALL Forms of Water, pp. 100-102. 

 (A., 1899.) 



1663. INFLUENCE, FAR-REACHING, 

 OF ONE GREAT MAN Roger Bacon the 

 Scientific Light of the Middle Ages. In all 

 that has directly operated on the extension 

 of the natural sciences, and on their estab- 

 lishment on a mathematical basis, and by 

 the calling forth of phenomena by the proc- 

 ess of experiment, Roger Bacon, the cotem- 

 porary of Albertus of Bollstadt, may be re- 

 garded as the most important and influen- 

 tial man of the Middle Ages. These two 

 men occupy almost the whole of the thir- 

 teenth century; but to Roger Bacon be- 

 longs the merit that the influence which he 

 exercised on the form of the mode of treat- 

 ing the study of Nature has been more bene- 

 ficial and lasting than the various discover- 

 ies which, with more or less justice, have 

 been ascribed to him. Stimulating the mind 

 to independence of thought, he severely con- 

 demned the blind faith attached to the au- 

 thority of the schools, yet, far from neglect- 

 ing the investigations of the ancient Greeks, 

 he directed his attention simultaneously to 

 philological researches, and the application 

 of mathematics and of the Scientia experi- 

 mentalis, to which last he devoted a special 

 section of the " Opus Majus." Protected 

 and favored by one pope ( Clement IV. ) , and 

 accused of magic and imprisoned by two 

 others (Nicholas III. and IV.), he experi- 

 enced the changes of fortune common to 

 great minds in all ages. HUMBOLDT Cosmos, 

 vol. ii, pt. ii, p. 245. (H., 1897.) 



1664, INFLUENCE FROM AFAR 



Attraction of the Sun for the Magnetic 

 Needle. It had long been noticed that dur- 

 ing the course of a single day the magnetic 

 needle exhibits a minute change of direction, 

 taking place in an oscillatory manner. And 

 when the character of this vibration came 

 to be carefully examined, it was found to 

 correspond to a sort of effort on the needle's 

 part to turn toward the sun. For example, 

 when the sun is on the magnetic meridian, 

 the needle has its mean position. This hap- 

 pens twice in the day, once when the sun is 

 above the horizon, and once when he is below 

 it. Again, when the sun is midway between 

 these two positions which also* happens 

 twice in the day the needle has its mean 

 position, because the northern and the 

 southern ends make equal efforts, so to 

 speak, to direct themselves toward the sun. 

 Four times in the day, then, the needle has 

 its mean position, or is directed toward the 

 magnetic meridian. But when the sun is 

 not in one of the four positions considered, 

 that ^end of the needle which is nearest to 

 him is slightly turned away from its mean 

 position, toward him. The change of posi- 

 tion is very minute, and only the exact 

 methods of observation made use of in the 

 present age would have sufficed to reveal it. 



