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THE POPULAR SCIENCE MONTHLY. 



of an epileptic seizure taking place suddenly 

 in an apparently healthy person is one of 

 such every-day occurrence that it scarcely 

 excites any notice. But if a medical witness 

 stands up in court and suggests that an 

 atrocious and apparently motiveless act of 

 violence was the insane act of the appar- 

 ently calm prisoner in the dock, he is in 

 danger of being ridiculed as a theorist." 



A Practical View of Parks.— Lord Bra- 

 bazon, at the Sanitary Congress held in York 

 in September, 1886, defended the propriety 

 of maintaining parks in large towns upon the 

 broadest practical grounds. Such establish- 

 ments, he held, should not be considered 

 luxuries, but public necessities. For health 

 is one of the first of necessities, and no ex- 

 pense should be spared, and no opportunity 

 neglected, to increase the average standard 

 of the nation's health and strength. If a 

 people's average standard of vitality be low- 

 ered, that people will assuredly be handi- 

 capped in the race of nations by as much as 

 that standard has been lessened. The health 

 of the mind is largely dependent on the 

 health of the body, and a nation can only 

 as have much muscular power and brain force 

 as may be the sum total of those qualities 

 possessed by the men and women of which it 

 is formed. It is an axiom of hygienic science 

 that, other things being equal, the health of 

 a population is in inverse ratio to its density. 

 Hence the density of population in large 

 towns should be offset by providing as much 

 open space as possible in the form of 

 squares, parks, and pleasure-grounds. 



Dangers of the laboratory. — A striking 

 instance of the dangerous quests which en- 

 thusiastic chemists undertake are the efforts 

 to investigate the yellow oily substance called 

 chloride of nitrogen. This terrible explosive 

 was discovered in 1811 by Dulong, who lost 

 one eye and three fingers in a vain attempt 

 to ascertain its composition. So powerful 

 is it that when Faraday and Sir Humphry 

 Davy took it in hand they provided them- 

 selves with thick glass masks to protect 

 their eyes from flying bits of glass, and to 

 some extent from the irritating vapors of 

 the oil itself. Faraday was on one occasion 

 stunned by a detonation of only a few grains 

 of the compound, and bits of the tube in 



which it had been contained almost pene- 

 trated his mask. On another occasion Sir 

 H. Davy was severely injured by the explo- 

 sion of a few drops under the receiver of 

 an air-pump. Since their time the precise 

 composition of the oil has been a mystery. 

 At last, however, Dr. Gattermann, of Got- 

 tingen, has succeeded in its analysis. He 

 finds that the substance examined hitherto 

 was impure, and that the extreme danger of 

 handling it was partly due to that fact, and 

 partly to the varying action of light. Any 

 bright light, he has found, is enough to pro- 

 duce detonation — a discovery made by the 

 sudden destruction of his apparatus by a 

 stray sunbeam. Chemical research nowa- 

 days is apt to stray among the teeming past- 

 ures of organic chemistry, to the neglect of 

 the old problems offered by the inorganic 

 world, though the solution of these problems 

 should enlist the highest efforts of experi- 

 mental science. 



Superstitions about Snakes. — Besides 

 certain errors in natural history, imagination 

 has vested snakes with some supernatural 

 or uncanny qualities. Thus, they are in 

 some places believed to know where buried 

 treasures are deposited ; to lie upon the 

 gold in winter ; and, while too wary to show 

 themselves near their hoard in summer, to 

 come out in the bright, warm days of spring 

 and bask in the neighborhood of their 

 winter quarters. At such times a wise man 

 will not kill them, but will watch where they 

 go, mark the place, and take measures to 

 possess himself of the treasure. But the 

 snake is supposed to fight wildly for his 

 property ; and there are feigned to be in 

 the old mines of Italy winged serpents which 

 never come into the open air, but haunt 

 the vaults where anything of value is hidden. 

 They live upon the scent of gold, and vio- 

 lently attack any one who forces his way 

 into their domain. No one, it is added, has 

 ever seen them except by torch-light, when 

 they must have looked rather like bats. The 

 house-snake in Carinthia is supposed to 

 bring good luck to the house he frequents. 

 The fatter he grows the fuller will be the 

 stalls, the granaries and the kitchen. So he is 

 not disturbed, but has a bowl of milk placed 

 every morning and evening in the cellar where 

 he lives. Some of these serpents are fabled 



