SCIENTIFIC SIDE-LIGHTS 



694 



mud of an ancient sea-bottom, but it is no 

 less certain that the chalk sea existed dur- 

 ing an extremely long period, tho we may 

 not be prepared to give a precise estimate 

 of the length of that period in years. 

 HUXLEY Lay Sermons, serin. 9, p. 189. (G. 

 P. P., 1899.) 



3433. TIME, IMMEASURABLE 

 LAPSE OF Ages Required to Build Chalk 

 Cliffs. The chalk . . . now seen stretch- 

 ing for thousands of miles over different 

 parts of Europe has become visible to us 

 by the effect, not of one, but of many dis- 

 tinct series of subterranean movements. 

 Time has been required, and a succession 

 of geological periods, to raise it above the 

 waves in so many regions. LYELL Princi- 

 ples of Geology, bk. i, ch. 10, p. 159. (A., 

 1854.) 



3434. TIME, INCREASING APPRE- 

 CIATION OF Our Indebtedness to Ages of 

 Thought and Observation. When we picture 

 to ourselves the virtuosity with which every 

 schoolchild is capable in our day of meas- 

 uring off and dividing uj> his time, and 

 how among our ordinary citizens the more 

 many-sided their life becomes in all direc- 

 tions, the more it is based upon an ever- 

 increasingly exact appropriation of time, 

 and that our modern great means of trans- 

 portation, the railroads and telegraphs, 

 scarcely reckon otherwise than according 

 to minutes, indicating thereby the exacti- 

 tude of their division of time, then it be- 

 comes difficult to transport our thoughts 

 back to that period when neither the for- 

 tunate nor the unfortunate had his hour. 

 And yet we still remember yonder blessed 

 childhood in which we, too, without regard 

 for time, measured off our entire career ac- 

 cording to nothing but days and nights, and 

 the great pleasures afforded by the festivals 

 of the year. And we still find byways, re- 

 mote from intercourse with great cities, 

 where a countryman will have no other 

 measure of time at his disposal than the 

 clock on the church tower of his hamlet, 

 and must regulate his hours of labor by the 

 course of the sun, the moon, or the stars. 

 Solitary shepherds are still to be met on 

 the heath who, in classic fashion, measure 

 time by the foot-lengths of their own shad- 

 ows. But who ever thinks, as he glances at 

 his watch or at a calendar condensed into 

 a few pages, of the thousands of years of 

 the most zealous astronomical observations 

 required to furnish both of these as we have 

 them in our day? Who ever considers that 

 this calendar, frequently coming to us in 

 such unpretentious garb, represents one of 

 the greatest achievements of human research 

 and effort? WITTICH Die Schnelligkeit un- 

 seres Empfindens und Wollcns (a Lecture), 

 p. 6. (Translated for Scientific Side-Lights. ) 



3435. TIME, LAPSE OF, MADE 

 SENSIBLE BY DWELLING ON IT Pre- 

 occupation Seems to Shorten. Our estimate 

 of time as it passes is commonly said to 



depend on the amount of consciousness which 

 we are giving to the fact of its transition. 

 Thus, when the mind is unoccupied and suf- 

 fering from ennui, we feel time to move 

 sluggishly. On the other hand, interesting 

 employment, by diverting the thoughts from 

 time, makes it appear to move at a more 

 rapid pace. This fact is shown in the com- 

 mon expressions which we employ, such as 

 " to kill time," and the German Langeweile. 

 Similarly, it is said that when we are eager- 

 ly anticipating an event, as the arrival of 

 a friend, the mere fact of dwelling on the 

 interval makes it appear to swell out. This 

 view is correct in the main. SULLY Illu- 

 sions, ch. 10, p. 250. (A., 1897.) 



3436. TIME, MAN'S FIRST MEAS- 

 URE OF Months and Weeks Determined by 

 the Moon. It was these phases and aspects 

 of the moon which formerly gave birth to 

 the custom of measuring time by months, 

 and by weeks of seven days, on account of 

 the return of the moon's phases in a month, 

 and because the moon appears about every 

 seven days, so to say, under a new form. 

 Such was the first measure of time; there 

 was not in the sky any signal of which the 

 differences, the alternations, and the epochs 

 were more remarkable. Families met to- 

 gether at a time fixed by some lunar phase. 

 FLAMMARION Popular Astronomy, bk. ii, 

 ch. 2, p. 100. (A.) 



3437. TIME OCCUPIED BY SENSA- 

 TION AND VOLITION Illustration of Whale 

 Wounded in the Tail. The time occupied 

 by a sensation and subsequent volition has 

 been measured in circumstances where there 

 were no conflicting impulses. This is done 

 by ascertaining the time elapsing between 

 the sensation of a signal and the answering 

 by the hand. A comparison is made between 

 two situations ; one where the person is pre- 

 pared beforehand, by knowing where he is 

 to be affected and what part is to move, in 

 which case the attention is turned upon the 

 proper points. The other situation is where 

 a person does not know which part is to be 

 struck, and which part is to be moved; in 

 this last case he has to exercise an active 

 judgment or consideration, and the differ- 

 ence of time is about the -^th of a second. 

 Two persons are separated by a screen; one 

 is to utter a syllable and the other to re- 



Ct it as soon as possible. If the syllable 

 been agreed upon, the interval of repe- 

 tition occupies from one- sixth to one- fourth 

 of a second; if it is not agreed upon, the 

 interval is one-twelfth of a second more. 

 The example is put by M. Du Bois Raymond 

 of a whale, ninety feet long, struck in the 

 tail by a harpoon; one second would be oc- 

 cupied in transmitting the impression to the 

 brain; a fraction of a second, say one- 

 tenth, in traversing the brain ; a full second 

 in returning the motor impulse, so that 

 the boat would have upward of two seconds 

 for escaping the danger. BAIN Mind and 

 Body, ch. 3, p. 10. (Hum., 1880.) 



