Exactness 



Expenditui 



SCIENTIFIC SIDE-LIGHTS 



232 



which serves as the unit of measurement for 

 the solar system and the whole stellar uni- 

 verse. WALLACE The Wonderful Century, 

 ch. 8, p. 60. (D. M. & Co., 1899.) 



1128. EXCESS OF CONCENTRATION 



Pure Waters Evaporated to Bitterness. 

 The streams flowing to the [Great Salt] lake 

 rise in the high mountains to the east and 

 are clear and limpid, and of such purity 

 that only chemical tests reveal the presence 

 of the mineral matter they have dissolved 

 from the rocks and soils. Several of these 

 streams are truly rivers in volume, as well 

 as in name, and send a never-ceasing flood 

 to the lake. Their combined volumes av- 

 erage throughout the year about 10,000 

 cubic feet per second. . . . None of the 

 springs supplying the lake, with a single 

 known exception, of small volumes, are 

 markedly saline. The salts they contain are 

 acquired largely during the upward passage 

 of the water through the sediment of former 

 lakes; and their influence on the chemistry 

 of the present lake is more important than 

 in the case of any other lake in the same 

 region. It is safe to conclude, however, that 

 the combined volumes of the streams and 

 springs now tributary to the lake, if not 

 concentrated by evaporation, would form a 

 water body in which no trace of saline mat- 

 ter would be apparent to the taste. RUS- 

 SELL Lakes of North America, ch. 4, p. 80. 

 (G. & Co., 1895.) 



1129. EXCESS OF INCREASE TENDS 

 TO EXTERMINATION The tendency to 

 multiply rapidly, so advantageous in normal 

 seasons, becomes almost fatal to a species 

 in seasons of exceptional abundance. Cover 

 and food without limit enabled the mice to 

 increase at such an amazing rate that the 

 lesser checks interposed by predatory species 

 were for a while inappreciable. But as the 

 mice increased, so did their enemies. In- 

 sectivorous and other species acquired the 

 habits of owls and weasels, preying exclu- 

 sively on them; while to this innumerable 

 army of residents was shortly added multi- 

 tudes of wandering birds coming from dis- 

 tant regions. No sooner had the herbage 

 perished, depriving the little victims of cover 

 and food, than the effects of the war became 

 apparent. In autumn the earth so teemed 

 with them that one could scarcely walk any- 

 where without treading on mice; while out 

 of every hollow weed-stalk lying on the 

 ground dozens could be shaken; but so rap- 

 idly had they been devoured by the trained 

 army of persecutors that in spring it was 

 hard to find a survivor, even in the barns 

 and houses. HUDSON Naturalist in La 

 Plata, ch. 3, p. 67. (C. & H., 1895.) 



1130. EXCITEMENT AN AID TO 

 FAITH Emotional Thrill Gives Sense of Re- 

 ality Terror on Precipice's Edge. Speak- 

 ing generally, the more a conceived object 

 (excites us, the more reality it has. The 

 eame object excites us differently at differ- 

 ent times. Moral and religious truths come 



" home " to us far more on some occasions 

 than on others. As Emerson says, " There is 

 a difference between one and another hour 

 of life in their authority and subsequent ef- 

 fect. Our faith comes in moments, . . . 

 yet there is a depth in those brief moments 

 which constrains us to ascribe more reality 

 to them than to all other experiences." The 

 " depth " is partly, no doubt, the insight 

 into wider systems of unified relation, but 

 far more often than that it is the emotional 

 thrill. Thus, to descend to more trivial ex- 

 amples, a man who has no belief in ghosts 

 by daylight will temporarily believe in them 

 when, alone at midnight, he feels his blood 

 curdle at a mysterious sound or vision, his 

 heart thumping, and his legs impelled to 

 flee. The thought of falling when we walk 

 along a curbstone awakens no emotion of 

 dread; so no sense of reality attaches to it, 

 and we are sure we shall not fall. On a 

 precipice's edge, however, the sickening emo- 

 tion which the notion of a possible fall 

 engenders makes us believe in the latter's 

 imminent reality, and quite unfits us to pro- 

 ceed. JAMES Psychology, vol. ii, ch. 21, p. 

 307. (H. H. & Co., 1899.) 



1131. EXEMPTION FROM ATTACK 

 INSURES INCREASE The Passenger-pigeon 

 The Fulmar Petrel. It is usually the 

 amount of destruction which an animal or 

 plant is exposed to, not its rapid multipli- 

 cation, that determines its numbers in any 

 country. The passenger-pigeon (Ectopistes 

 migratorius) is, or rather was, excessively 

 abundant in a certain area in North 

 America, and its enormous migrating flocks 

 darkening the sky for hours have often been 

 described; yet this bird lays only two eggs. 

 The fulmar petrel exists in myriads at St. 

 Kilda and other haunts of the species, yet it 

 lays only one egg. . . . Some of the 

 grasses and sedges, the wild hyacinth, and 

 many buttercups occur in immense profu- 

 sion over extensive areas, altho each plant 

 produces comparatively few seeds. WAL- 

 LACE Darwinism, ch. 2, p. 20. (Hum., 1889.) 



1132. EXPANSION EXPLAINED AS 

 VIBRATION Planet Viewed through Heated 

 Air. But how are we to picture such dila- 

 tation [expansion by heat] in accordance 

 with the theory which regards heat as a 

 mode of motion? The comparison of a very 

 great thing with an indefinitely small one 

 will here help us to a clear conception. I 

 once approached Gibraltar on a fine star- 

 light night when the planet Jupiter was 

 sharply defined on a clear sky. On walking, 

 however, past the funnel of the steamer, so 

 as to bring the heated air between me and it, 

 the planet suddenly augmented in apparent 

 size, losing at the same time part of its 

 sharpness of definition. The expansion was 

 evidently due to the heated air, causing the 

 image of the planet to quiver on the retina. 

 This quivering was in all directions, and it 

 was so rapid that the various motions 

 blended upon the retina to a disk of aug- 



