Curiosities of Science. 19 



evaporation of water, for instance from the widely-spreading 

 ocean ; how the clouds produced by this pass over into foreign 

 lands and then fall again to the earth as rain, and how this 

 wandering water is, partly at least, carried along new journeys, 

 returning after various voyages to its original home : the mere 

 mechanical phenomena, such as the transfer of seeds by the 

 winds or by birds, or the decomposition of the surface of the 

 earth by the friction of the elements, suffice to illustrate this." 



TIME AN ELEMENT OF FOKCE. 



Professor Faraday observes that Time is growing up daily 

 into importance as an element in the exercise of Force, which 

 he thus strikingly illustrates : 



The earth moves in its orbit of time ; the crust of the earth moves in 

 time ; light moves in time ; an electro-magnet requires time for its charge 

 by an electric current : to inquire, therefore, whether power, acting either 

 at sensible or insensible distances, always acts in time, is not to be me- 

 taphysical ; if it acts in time and across space, it must act by physical 

 lines of force ; and our view of the nature of force may be affected to 

 the extremest degree by the conclusions which experiment and obser- 

 vation on time may supply, being perhaps finally determinate only by 

 them. To inquire after the possible time in which gravitating, magnetic, 

 or electric force is exerted, is no more metaphysical than to mark the 

 times of the hands of a clock in their progress ; or that of the temple of 

 Serapis, and its ascents and descents ; or the periods of the occultation 

 of Jupiter's satellites; or that in which the light comes from them to 

 the earth. Again, in some of the known cases of the action of time 

 something happens while the time is passing which did not happen be- 

 fore, and does not continue after ; it is therefore not metaphysical to 

 expect an effect in every case, or to endeavour to discover its existence 

 and determine its nature. 



CALCULATION OF HEIGHTS AND DISTANCES. 



By the assistance of a seconds watch the following inter- 

 esting calculations may be made : 



If a traveller, when on a precipice or on the top of a building, wish 

 to ascertain the height, he should drop a stone, or any other substance 

 sufficiently heavy not to be impeded by the resistance of the atmosphere ; 

 and the number of seconds which elapse before it reaches the bottom, 

 carefully noted on a seconds watch, will give the height. For the stone 

 will fall through the space of 16J feet during the first second, and will 

 increase in rapidity as the square of the time employed in the fall : if, 

 therefore, 16j be multiplied by the number of seconds the stone has 

 taken to fall, this product also multiplied by the same number of seconds 

 will give the height. Suppose the stone takes five seconds to reach the 

 bottom : 



16^ x 5=80| x 5=403&, height of the precipice. 



The Count Xavier de Maistre, in his Expedition nocturne autoiir de 

 ma Ckambre, anxious to ascertain the exact height of his room from the 

 ground on which Turin is built, tells us he proceeded as follows : " My 

 heart beat quickly, and I just counted three pulsations from the instant 



