Show I L WHAT a DROP in the BUCKET Really LOOKS LIKE a n drop in fn the bucket i is a familiar an and JUST use useful ul simile but it remained for an English J schoolboy to wonder what happens when the tho drop strikes in the bucket How he tried to find out by causing drops to fall upon carefully smoked glass after which he could study the prints I made by the drop upon the carbon is de described de de- scribed in Popular Science Monthly by H. H E. E Howe Some twenty years ears later Prof A A. M. M Worthington became interested in drops and in 1894 under the title The Splash o of a Drop delivered delivered de de- livered an address setting forth his observations This was afterward printed by the Royal Roal It certain that any ariy changes chang s that a drop undergoes must be of exceedingly short duration II g- g Surface tension causes the gymnastic c exercises exercises exer exer- cr that a drop goes through when it falls writes Mr Howe Home Hence the first problem as 5 in most investigations was that involved in providing pro pro- viding riding idin suitable apparatus A drop rop of definite size was vas to be allowed to fall from a definite height in darkness and any desired stage in the phenomenon illuminated by a spark of such exceedingly exceedingly ex ex- ly short duration that all other stages would remain unobserved and not blur the picture These conditions were eventually satisfied by providing two similar levers released by an electromagnet From Fiona one lever th the drop was allowed to fall from a small watch glass smoked to prevent wettin wetting and the other let fall falla a marble ma that struck an adjustable releasing mechanism which in turn broke which an electrical connection con con- causing a short park near the spot where the drop struck rop By regulating the release re release re- re lease mechanism and therefore the distance through 11 which the marble fell feU intervals sepa sepa- rated by very small fractions of a n second could be secured At the time the first experiments were made the photographic plate was not sufficiently rapid to record the image so that Prof Worthington found it necessary to make a very large number of observations of each stage until he could accurately ac acv sketch what he had seen Later on he had the satisfaction o of being able to confirm his hla early work using more modern photographic apparatus apparatus apparatus ap ap- and fast emulsions The illustrations reproduced hero here ar are arc from froma a series of drawings and show tho the exercise a drop of mercury takes when one 16 15 inch la is diameter falls three inches upon a a. smooth glass plate Surface tension is responsible for the move move- movements movements ments meats and patterns observed The distinct rays s a v. v II a lIa As the drop spreads it H forms distinct rays rays rays- sometimes as many as twenty-four twenty Fig 9 II r. r J s Forming pairs of lobes Fig 17 with twelve pairs is the climax of this stage mo II The surface tension checks the spread of tf f the drop and causes the centre to rise shown in No 0 9 arc 24 in number as determined by counting the droplets that squeeze off the end of these rays Next an annulus with a n very thin area between centre and rim is formed followed by the rim form forming ins pairs of or lobes These are drawn together until in stage 17 we find 1 12 lobes Surface tension checks the spread and then thena a rapid and power powerful ul contraction takes place causing the mercury to rise in the centre almost to the breaking point as in 26 This sudden drawing draving in of or the lobes causes droplets to become dc detached and marks the bc beginning of the re rev bound At the end ncI we mu may have two circles s of different sized drops surrounding the remainder of the original drop and the entire entin series of 30 sta stages c takes lakes place in a total time of about one- one twentieth of oC a second second un an interval of oC one oUt s six six- th of a second for fOl each stage At A t certain stages such as numbers 14 15 n Sort It r. r 1 IDO and nd 16 the mercury is sometimes covered with wit beautiful concentric rings The liThe phenomenon depends upon four fac factors l 1 The size of the drop 2 The height of the fall 3 The surface tension of f the liquid in ia question 4 The viscosity of the liquid The possibilities of this interesting study have by no means become ome exhausted Study drops of ink or of milk falling upon water or indeed the phenomenon of large drops o of water falling faIling upon water giving rise to the beautiful ul bubbles EO so often seen in a hard rain min Solids falling into liquids are another possibility Modern photography photography remember remember that Prof Proto Worthington did his work before 1894 1894 ought ought to record unusual features feature He used wed a Leyden Jar ju II 1111 1111 The rebound Only one twentieth of a second intervened between between between be be- tween Figs 1 and 30 spark for his photography the duration of or such sucha a n spark being probably less than ten millionths of ot a second |