FRAGMENTS OF SCIENCE. 



103 



cinal preparation above mentioned is ob- 

 tained in this way, and represents a 

 fairly pure form of the diastatic prin- 

 ciple. This bears the name of ' taka- 

 diastase.' " 



Professor Agassiz's Investiga- 

 tions on Coral Islands. — Having 

 steamed and observed for twenty-five 

 hundred miles among the Paumotu Is- 

 lands, Prof. Alexander Agassiz says, in 

 a second letter from the Albatross Ex- 

 pedition, published in the American 

 Journal of Science, that he has seen 

 nothing tending to show that there has 

 anywhere been a subsidence, but that 

 the condition of the islands does not 

 seem to him capable of explanation on 

 any theory except that they have been 

 formed in an area of elevation. All the 

 islands examined are composed of a ter- 

 tiary coralliferous limestone, which has 

 been elevated to a greater or less extent 

 above the level of the sea, and then 

 planed down by atmospheric agencies 

 and submarine erosion, and the appear- 

 ance of this old rock is very different 

 from that of the modern reef rock. In 

 these islands the rims of the great 

 atolls, after having been denuded to the 

 level of the sea, are built up again from 

 the material of their two faces, so that 

 a kind of conglomerate, or breccia, or 

 pudding stone, or beach rock is found on 

 all the reef flats. On the lagoon side 

 sand bars grow into small islands and 

 gradually become covered with vegeta- 

 tion. Whenever the material supplied 

 from both sides is very abundant the 

 land ring becomes more or less solid; 

 the islets become islands, separated by 

 narrow or wider cuts, until they at 

 length form the large islands, which 

 seem at first to be a continuous land 

 around the rim of the lagoon, while 

 they are often really much dissected. In 

 time water ceases to pass through the 

 channels, and only the marks of them 

 are left. Few if any of the lagoons ap- 

 pear to be shut off from the sea, as Dana 

 and other writers have supposed. They 

 simply have not boat passages. Unlike 

 other coral regions, the Paumotu reefs 

 seem to bear only a scanty life. 



"Winking." — No satisfactory de- 

 termination has been made of the reason 

 we wink. Some suppose that the de- 

 scent and return of the lid over the eye 



serves to sweep or wash it off; others 

 that covering of the eye gives it a rest 

 from the labor of vision, if only for an 

 inappreciable instant. This view bor- 

 rows some force from the fact that the 

 record of winking is considerably used 

 by experimental physiologists to help 

 measure the fatigue which the eye suf- 

 fers. In another line of investigation 

 Herr S. Garten has attempted to meas- 

 ure the length of time occupied by the 

 different phases of a wink. He used a 

 specially arranged photographic appa- 

 ratus, and affixed a piece of white paper 

 to the edge of the eyelid for a mark. 

 He found that the lid descends quickly, 

 and rests a little at the bottom of its 

 movement, after which it rises, but 

 more slowly than it fell. The mean du- 

 ration of the downward movement was 

 from seventy-five to ninety-one thou- 

 sandths of a second; the rest with the 

 eye shut lasted variously, the shortest 

 durations being fifteen hundredths of a 

 second with one subject and seventeen 

 hundredths with another; and the third 

 phase of the wink, the rising of the lid, 

 took seventeen hundredths of a second 

 more, making the entire duration of the 

 wink about forty hundredths, or four 

 tenths of a second. The interruption is 

 not long enough to interfere with distinct 

 vision. M. V. Henri says, in L'Annee 

 Psychologique, that different persons 

 wink differently — some often, others 

 rarely; some in groups of ten or so at 

 a time, when they rest a while; and 

 others regularly, once only at a time. 

 The movement is modified by the degree 

 of attention. Periods of close interest, 

 when we wink hardly at all, may be fol- 

 lowed by a speedy making up for lost 

 time by rapid winking when the tension 

 is relieved. 



An Ingenious Method of Locat- 

 ing an Obstruction.- — The Engineer- 

 ing Record gives the following interest- 

 ing account of the scientific solving of 

 a practical commercial problem : " The 

 pneumatic dispatch tube for the deliv- 

 ery of mail between the main Philadel- 

 phia post office and a branch office at 

 Chestnut and Third Streets is a cast- 

 iron pipe buried below the surface of 

 the street, and in it small cylindrical 

 carriers, six inches in diameter, are pro- 

 pelled from end to end by air pressure. 

 At one time a carrier became lodged at 



