SCIENCE SIFTINGS

New Zealand Tablet, 24 November 1921, Page 46

SCIENCE SIFTINGS

: ■ ;: : : 4[ -; T r' By '* VOLT** -J, >II :: 7.P^=

li, ,' u „ ' ~ i ii- ——^-»- —y ■.;■■•■'*.>' "'■ - -■'•"' ' ," ■••" •'■"'■■ -' : ' -■■'*- -.'■. v- ■■•^V v -f-':;••/'.'"■" 7 f/s"'/-;".-- : ' ' -TELLING m THE TIME AT -SEA. 'V v --'" : ?>-- ; -~r ■■:■■ The sailor's day is divided into ; watches of, four ; hours each. ' , ' , „~ These begin at four, eight, and twelve o'clock, day and night; and every half-hour of the i watch 'is signalled by the < striking of the ship's bell. '. r : ".'Z ■..''.,■■' ". ! . .'V 7* By night or by day, four o'clock, eight : o'clock, and twelve o'clock; are known as eight bells. ;' Then, beginning at the next , half-hour, one bell is struck ; the following'half--hour two bells are struck; at the next, three; 'and so on up to eight bells, when a new watch begins. >'• . f: ; r,' v.; For instance: eight a. m. is recorded by eight bells, half-past eight by one bell, nine o'clock by two bells, halfpast nine by three bells, ten o'clock by four bells, halfpast ten by five bells, eleven o'clock by. six bells; half-past eleven by seven bells, and twelve o'clock (noon), by eight bells. ' ' "' r ' " During the next watch (from midday to four p.m.) this formula is repeated, beginning with one bell at halfpast twelve, and so on. . ' ""' '"'.'. , cuts THAT MEANT cash. Z.i'Zy.'■■."The days of our age are threescore years and ten," said the Psalmist, showing that our forefathers reckoned by scores, a system of keeping account of figures based probably in its original form upon the practice of counting upon the fingers and toes. , . ; The word "score" itself comes from the Anglo-Saxon, being nothing more than the word "scoren," which is the past participle of "sceran" —meaning to cut. It indicated a notch or incision .made upon a tally-stick for the purpose of keeping a record of financial; transactions. Z'i The "score-mark" was the twentieth notch upon these primitive "account books"—a cut which was longer and deeper than the others! Hence the 'expression, "to pay off old scores," means not only the repayment of old debts, but the revenging of grievances 1 which have cut deep and left a lasting impression. '" "' < '' °* ' '""' *,v ir ' It is for the same reason, that of reckoning, that we speak of the "score'' of a game—meaning the record of the points made—and the "score" or musical record of an opera.; ; "' '-'..'-"' : .'■: ' "'' y _",»*' , /*. r-, _ WHEN THE SEA BULGES. The rise and fall of largei-'" bodies of water—a phenomenon to which we ; have applied the name of tides—is the result of the influence exerted upon the earth by the moon and sun. ' •<■''■■' / v n l

Both pull or attract the earth in varying degrees, the power of the moon being about two and a quarter times as great as that of the sun. This attraction is most evident in the fluid portion of the earth’s surface-r-the oceans and larger lakes, which are so affected that they bulge outward, forming a rising of the water on the side of the earth nearest the moon, and also on the opposite side, with corresponding low . water between,' / _ :

The reason for extreme high tides at the times of the new and full moon is because the moon is then in a line with the sun, and the water reacts to the combined pulls of both bodies; At ‘ the time of the first and third quarters of the. moon this influence/ is divided single-unit pull of the sun acting at right angles to the two and a quarter unit pull of the moon, thus diminishing materially , the attraction exerted upon the earth and producing tides that do not rise nearly as high as the ones occurring .’ during the times of the full or new moon. ' ,

As the moon appears to revolve about ,the earth once every.. 24 hours and- 48 minutes, two tidal waves continually sweep around ; beneath, her, causing two high ; tides and two low tides in each approximate, day. :: ,v; v *