tion 

 scovery 



SCIENTIFIC SIDE-LIGHTS 



172 



gested matter being afterwards absorbed. 

 This fact, which will be clearly proved, is a 

 wonderful one in the physiology of plants. 

 DARWIN Insectivorous Plants, ch. 6, p. 71. 

 (A., 1900.) 



837. DIRECTION, SENSE OF, IN 

 BEES AND WASPS Difficulty of Learning 

 by Experience. The following are Sir John 

 Lubbock's [Lord Avebury's] observations 

 upon this subject in the case of bees and 

 wasps : 



" Every one has heard of a ( bee-line.' It 

 would be no less correct to speak of a wasp- 

 line. On August 6 I marked a wasp, the 

 nest of which was round the corner of the 

 house, so that her direct way home was not 

 out at the window by which she had entered, 

 but in the opposite direction, across the 

 room to a window which was closed. I 

 watched her for some hours, during which 

 time she constantly went to the wrong win- 

 dow, and lost much time in buzzing about 

 at it. For ten consecutive days this wasp 

 paid numerous visits, coming in at the open 

 window, and always trying, tho always un- 

 successfully, to return to her nest in the 

 ' wasp-line ' of the closed window buzzing 

 about that window for hours at a time, tho 

 eventually on finding it closed she returned 

 and went round through the open window 

 by which she always entered." 



This observation shows how strong must 

 be the instinct in a wasp to take the short- 

 est way home, and how much the insect de- 

 pends upon its sense of direction in so doing. 

 It also shows how long a time it requires to 

 learn by individual experience the proper- 

 ties of a previously unknown substance, such 

 as glass. ROMANES Animal Intelligence, ch. 

 4, p. 144. (A., 1899.) 



838. DIRECTNESS OF RAYS OF 

 LIGHT Ancients Knew the Rectilinear Propa- 

 gation of Light Hence the Terms " Ray " 

 and " Beam" The ancients were aware of 

 the rectilinear propagation of light. They 

 knew that an opaque body, placed between 

 the eye and a point of light, intercepted the 

 light of the point. Possibly the terms 

 " ray " and " beam " may have been sug- 

 gested by those straight spokes of light 

 which, in certain states of the atmosphere, 

 dart from the sun at his rising and his set- 

 ting. The rectilinear propagation of light 

 may be illustrated by permitting the solar 

 light to enter, by a small aperture in a win- 

 dow-shutter, a dark room in which a little 

 smoke has been diffused. In pure air you 

 cannot see the beam, but in smoke you can, 

 because the light, which passes unseen 

 through the air, is scattered and revealed by 

 the smoke particles, among which the beam 

 pursues a straight course. TYNDALL Lec- 

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



839. DISASTER LEADS TO DISCOV- 

 ERY Exploaiveness of Niter Demonstrated. 

 The first published contribution to chemis- 

 try [under the auspices of the Smithsonian 



Institution] was the " Memoir on the Ex- 

 plosiveness of Niter," by Robert Hare. 

 . . . Its history is interesting. A fire 

 occurred in New York City on July 19, 1845, 

 during which two hundred and thirty houses 

 were destroyed, containing merchandise 

 valued at over two millions of dollars. A 

 peculiar feature of this catastrophe was a 

 series of detonations successively increasing 

 in loudness, and followed by a final explo- 

 sion which tore in pieces the building where 

 it occurred, threw down several houses in 

 the vicinity, and forced in the fronts of 

 houses on the opposite side of the street. 

 These effects were attributed to gunpowder, 

 but the owner of the building declared that 

 he had none of that explosive, altho a large 

 quantity of niter was stored in the house. 

 Dr. Hare showed by numerous experiments 

 that explosions of a violent character could 

 be produced by forcibly bringing in contact 

 at a high temperature niter and substances 

 of an inflammable character. MARCUS BEN- 

 JAMIN Chemistry in the Smithsonian Insti- 

 tution, History of the First Half Century, 

 p. 612. 



840. DISASTER, POSSIBLE, MAN 

 PROVIDES AGAINST Houses Built to With- 

 stand Earthquakes. In South America, al- 

 tho many buildings are built with brick and 

 stone, the ordinary houses, and even the 

 larger edifices, are specially built to with- 

 stand earthquakes. In Mr. James Douglas's 

 account of a "Journey Along the West 

 Coast of South America," we read the fol- 

 lowing : " The characteristic building ma- 

 terial of Guayaquil is bamboo, which grows 

 to many inches in thickness, and which, 

 when cut partially through longitudinally 

 at distances of an inch or so, and once quite 

 through, can be opened out into fine elastic 

 boards of serviceable width. Houses, and 

 even churches, of a certain primitive beauty 

 are built of such reeds, so bound together 

 with cords that few nails enter into the con- 

 struction, and which, therefore, yield so 

 readily to the contortions of the earth dur- 

 ing an earthquake as to be comparatively 

 safe." MILNE Earthquakes, ch. 7, p. 126. 

 (A., 1899.) 



841. DISCOVERER OF BACTERIA 



Plain Business Man Makes His Own Lenses 

 Advances Microscopy. The first scientist 

 who demonstrated the existence of micro- 

 organisms was Anton van Leeuwenhoek. 

 He was born at Delft, in Holland, in 1632, 

 and enthusiastically pursued microscopy 

 with primitive instruments. He corrobo- 

 rated Harvey's discovery of the circulation 

 of the blood in the web of a frog's foot; he 

 defined the red blood-corpuscles of verte- 

 brates, the fibers of the lens of the human 

 eye, the scales of the skin, and the structure 

 of hair. He was neither educated nor 

 trained in science, but in the leisure time of 

 his occupation as a linen-draper he learned 

 the art of grinding lenses, in which he be- 

 came so proficient that he was able to con- 

 struct a microscope of greater power than 



