147 



SCIENTIFIC SIDE-LIGHTS 



truncated cone. On the summit, as we learn 

 from Plutarch, there was a crater with 

 steep clifl's, and having its interior over- 

 grown with wild vines, and with a sterile 

 plain at the bottom. On the exterior, the 

 flanks of the mountain were clothed with 

 fertile fields richly cultivated, and at its 

 base w r ere the populous cities of Hercu- 

 laneum and Pompeii. But the scene of re- 

 pose was at length doomed to cease, and the 

 volcanic fire was recalled to the main chan- 

 nel, which at some former unknown period 

 had given passage to repeated streams of 

 melted lava, sand, and scoriae. LYELL Ge- 

 ology, ch. 23, p. 363. (A., 1854.) 



722. DANGER-SIGNALS AMONG 



ANIMALS Warning Coloration a Defense to 

 Its Possessor. [Some colorations] are de- 

 veloped for the express purpose of rendering 

 the species conspicuous. The reason of this 

 is that the animals in question are either 

 the possessors of some deadly weapons, as 

 stings or poison-fangs, or they are uneat- 

 able, and are thus so disagreeable to the 

 usual enemies of their kind that they are 

 never attacked when their peculiar powers 

 or properties are known. It is, therefore, 

 important that they should not be mistaken 

 for defenseless or eatable species of the same 

 class or order, since in that case they might 

 suffer injury, or even death, before their 

 enemies discovered the danger or the use- 

 lessness of the attack. They require some 

 signal or danger-flag which shall serve as a 

 warning to would-be enemies not to attack 

 them, and they have usually obtained this in 

 the form of conspicuous or brilliant colora- 

 tion, very distinct from the protective tints 

 of the defenseless animals allied to them. 

 WALLACE Darwinism, ch. 9, p. 158. (Hum., 

 1889.) 



723. DANGERS FACED BY SCIEN- 

 TISTS "Mountain Sickness" Rarefied Air 

 May Be Fatal. The years brought round 

 the eclipse of 1878, which was again in 

 United States territory, the central track 

 running directly over one of the loftiest 

 mountains of the country, Pike's Peak, in 

 Colorado. Pike's Peak, tho over fourteen 

 thousand feet high, is often ascended by 

 pleasure tourists; but it is one thing to 

 stay there for an hour or two, and another 

 to take up one's abode there and get accli- 

 mated for to do the latter we must first 

 pass through the horrors (not too strong a 

 word) of mountain sickness. This reaches 

 its height usually on the second or third 

 day, and is something like violent seasick- 

 ness, complicated with the sensations a 

 mouse may be supposed to have under the 

 bell of an air-pump. After a week the 

 strong begin to get over it, but none but the 

 very robust should take its chances, as we 

 did, without preparation; for on the night 

 before the eclipse the life of one of our little 

 party was pronounced in danger, and he was 

 carried down in a litter to a cabin at an 

 altitude of about ten thousand feet, where 



he recovered so speedily as to be able to do 

 good service on the following day. LANG- 

 LEY 2V 7 ew Astronomy, ch. 2, p. 50. (H. M. & 

 Co., 1896.) 



724. DANGERS OF ISOLATION No 

 Man Sufficient to Himself The Corrective 

 of Society a Necessity for Sound Thinking. 

 Neither is such a practise [of devoting 

 oneself wholly to thinking and teaching 

 without reading or study], in a hygienic 

 point of view, free from the gravest dangers 

 to the philosopher's own mind. When once 

 he has persuaded himself that he can work 

 out the final truth on any subject, exclusive- 

 ly from his own sources, he is apt to lose all 

 measure or standard by which to be apprised 

 when he is departing from common sense. 

 Living only with his own thoughts, he 

 gradually forgets the aspect they present to 

 minds of a different mold from his own ; he 

 looks at his conclusions only from the point 

 of view which suggested them, and from 

 which they naturally appear perfect; and 

 every consideration which from other points 

 of view might present itself, either as an ob- 

 jection or as a necessary modification, is to 

 him as if it did not exist. When his merits 

 come to be recognized and appreciated, and 

 especially if he obtains disciples, the intel- 

 lectual infirmity soon becomes complicated 

 with a moral one. The natural result of the 

 position is a gigantic self-confidence, not to 

 say self-conceit. MILL Positive Philosophy 

 ofAugusteComte,p.U7. (H.H. & Co.,1887.) 



725. DARKNESS ATTENDED WITH 



COLD Night for Five Months. One of the 

 last expeditions made for the discovery of 

 the north pole that of the English navi- 

 gators Nares and Stephenson (May 29, 1875, 

 to November 2, 1877) which advanced 

 farther than any of its predecessors up to 

 82 24' had 142 days of solar privation 

 nearly five months of night! From Novem- 

 ber 6 to February 6 the night was complete 

 and dark. Even on November 8 the dark- 

 ness was so complete at noon that it was 

 impossible to read. But soon the moon 

 brought a reflection of the vanished sun, 

 and turned round the pole without ever set- 

 ting for ten times twenty-four hours. The 

 thermometer went down to 58 centigrade 

 below zero ! ( It has been seen still lower at 

 Werchojansk, in Siberia 68.) These low 

 temperatures are never accompanied with 

 wind; otherwise no human being could 

 stand such cold. icy solitudes of the pole, 

 you have already received heroes who have 

 lain down forever in your gloomy shroud! 

 The road to the pole is always marked with 

 martyrs; but it is not the odious war of 

 man against man: it is the triumph of 

 mind over matter, the conquest of Nature by 

 genius! FLAMMAEION Popular Astronomy, 

 p. 31. (A.) 



726. DARKNESS BEFORE DAWN 



OF NEW ERA Summary of Human Knowl- 

 edge of the Stars through All Centuries 

 before 1775. A star in the Swan was per- 



