Supplement to ''Nature'' November 24, 1923 



-¥«— 



Wagstaff's 



Apparatus for Timing a Falling Body 



(Provisionally Protected) 



The apparatus shown in the diagram is designed to find by a direct experimental method the time a body takes 

 to fall a specified distance. The result is accomplished by making the time of fall synchronise with a half period of 

 vibration of an adjustable pendulum D. 



The falling body is dropped from an electromagnet A, when the energising circuit is broken by the pendulum 

 passing through the middle position. 



The body falls upon a platform B, which moves up and down on a vertical 

 standard. The impact breaks momentarily one arc of a second circuit, the other 

 arc of which passes through a connection C governed by the pendulum, and is 

 broken each time the pendulum passes the mid-position. These two arcs in parallel 

 are joined in series with a bell, which sounds only when the currents in both the 

 arcs are broken simultaneously. 



The body is thus released by the first passage of the pendulum in the mid'posi- 

 tion. If the body strikes the platform at the instant when the pendulum again passes 

 the mid'position the bell F rings. When this occurs, the time of fall must be equal 

 to the half-vibration period of the pendulum. The pendulum can be timed by a 

 watch; the height of fall is measured on the scale on the standard. 

 From these results " g " is calculated. 



The apparatus is in two parts. One is a Standard with a five-foot scale, by 

 which the position of the moveable platform can be regulated. 



The other portion carries the pendulum, and the bell which sounds when the 

 platform is in the correct position. 



The necessary connections are supplied, and are so arranged that it is impossible 

 to connect up wrongly. 



The general idea of the machine will be gathered from the accompanying 

 diagram. The adjustments are readily made, and the results obtainable remarkably 

 accurate. An error of liii second is possible and one of to^oit second is usual; 

 though the machine is not designed to attain a greater accuracy than this, results are 

 often obtained which are not in error by to'^tt second. 



PARTICULARS 



APPLY TO: 



W. G. PYE & CO. 



GRANTA WORKS, CAMBRIDGE. ENG. 



Makers of Physical, Electrical, Scientific and Wireless Apparatus. 



SECOND-HAND TELESCOPES 



4-inch Cooke, with finder, on Graduated Equatorial, clock, iron 

 column, and extremely stable tripod, star diagonal, many eyepieces, 

 fitted cases, perfect condition £110 O 



4-inch Watson Royal Century, large finder, i day, 3 astros. , dew 

 shade, in mahogany case. Equatorial Head, with 6-inch divided l)rass 

 circles, adjustable oak stand. £65 O 



3-inch Wray, finder, ve.'tical rack, day, 2 astrcs. and diagmial eye- 

 pieces, open frame garden stand. £22 10 O 



SECOND-HAND MICROSCOPES 



Swift '' Army," 2 eyepieces, |", J", -j',^" O.I. objectives, triple nose- 

 piece, racking substage. Abbe and iris. £17 10 O 

 Zeiss Stand VI, centring no.sepiece, revolving divided stage, 2 eye- 

 pieces, A and J) objectives, £11 10 O 

 Many others by all makers; lists on application. 



CLARKSON'S, 338 High Holborn, London, W.C.I. 



Opposite Gray's Inn Roarj. (The Original Firm.) Phone: Ilolborn .m.((). 



DISTILLED WATER 



Brown's Stills are perfectly auto- 

 matic. Can be run night and day 

 without attention. Patented in U.K. 

 and Continental Countries. Extra- 

 ordinarily efficient and economical. 

 Made for gas, steam, oil, or coke-fire 

 heating. 



Full fiartiiulars and (•> ices frci- ,^n .'//.'/. .i.',,'« 



BROWN & SON 



ALEMBIC WORKS 



WEDMORE ST., HOLLOWAY, 



LONDON, N 19. 



Notice, 



The lecture by Prof. N. Bohr on " The Structure of the Atom," 

 hitherto obtainable in pamphlet form, is now out of print. 



*,* A list of the Nos. of NATURE containing special supplements and still in print 



will be sent upon application. 



Office of NATURE, St. Martin's Street, W.C.2. 



