360 



♦ KNOWLEDGE ♦ 



[Oct. 31, 1884. 



'burning the thread, as Guglielmini had done, lest slight 

 draughts of air thus occasioned might cause the ball to 

 oscillate before being detached. The mode of liberation he 

 actually employed was ingeniously devised to prevent the 

 balls from being in any way influenced by the act of libera- 

 tion. The suspending thread passed through a vertical 

 aperture in a block, aud was elapsed above by nipper.'', 

 opening in an horizontal plane. 



He dropped, first, a number of balls experimentally, to 

 gauge the requirements of the problem. At last, when all 

 the arrangements had been made which these expeiiments 

 suggested, he dropped 31 balls. Of these 



21 fell towards the east. 

 8 ditto west. 



2 neither towards the east nor west. 



16 fell towards the south. 



1 1 ditto north. 



4 fell neither towards the south nor north. 



The actual deviations carefully summed gave the follow- 

 ing results : — 



Sum of deviations towards the north 464 lines, 



Ditto ditto south 92 6 ditto 



Ditto ditto east 174-5 ditto 



Ditto ditto west 505 ditto 



Balance of deviations towards the south 46 2 ditto 



Ditto ditto east 124-0 ditto 



As there should be no deviation towards the south, we 

 must take the observed deviation in that direction as 

 measuring the probable errors in the series of experiments. 

 This leaves to be accounted for an obvious tendency 

 towards the east — that is, in the direction according with 

 the theory of the earth's rotation. The mean deviation 

 1 94. 



towards the east is _^, or four lines. Calculation shows 

 31 



that the mean deviation should have been 3-85 lines, so 

 that theory and observation agreed very closely. 



But Benzenberg thought the southerly deviation too 

 considerable to render his experiments satisfactory. He 

 therefore made new experiments in an abandoned coal-pit 

 at Schlebusch, in Westphalia, with an available fall of 

 :S62 ft. He carefully covered the entrance of the pit, and 

 blocked up all its lower passages before commencing hi.s 

 experiments. He then dropped twenty-nine balls. The 

 results were as follows : — 



Sum of deviations towards the north, 124 lines 

 Ditto ditto south, 103 ditto 



Ditto ditto east, 189 ditto 



Ditto ditto west, 42 ditto 



or a mean northern deviation of 7 lines and a mean 

 easterly deviation of 5 1 lines. The calculated easterly 

 deviation for a fall of 202 it. is 4 6 lines ; so that in this 

 experiment, as in the preceding, theory and observation 

 agreed very closely together. As in these experiments, 

 also, a balance of deviation towards the north was observed, 

 while in the former the balance of deviation was towards 

 the south, we see the more reason to regard northerly and 

 southerly deviations as the result of those errors which can 

 never be altogether avoided in experiments of the sort. 



Lastly, a long and most convincing series of experiments 

 was carried out on the same plan by Professor Reich in the 

 mines of Freiburg. He was able to drop balls to a depth 

 of no less than 488 fc, and he made no less than 106 ex- 

 periments. There was a balance of southerly deviation of 

 48-76 lines, and a balance of easterly deviation of 109392 

 lines ; so that the mean deviation towards the south was 

 but 0-46 lines, while the mean deviation towards the east 

 was 10-32 lines. 



Here, then, we have in all a series of 166 experiments, 



with a result pointing very definitely to an easterly devia- 

 tion in bodies falling from a great height. We are com- 

 pelled to conclude that this cannot be accidental. It must 

 arise from some real cause or other. The earth's rotation 

 accounts most satisfactorily for it, whereas no other ex- 

 planation seems to suggest itself as even possibly explain- 

 ing the phenomenon. Thus we are again led to the 

 conclusion that the earth rotates upon its axis from west 

 to east.* 



The evidence of the earth's rotation, derived from the 

 oscillations of a free pendulum, is also .singularly powerful 

 and interesting. But this has been already fully considered 

 in a former number (see Knowledge, June 0, 1884, p. 413.) 



I 



MATCH-LORE. 



N Shelley's wonderful version of the Homeric Hymn to 

 Mercury, we learn that 



Mercury first foond out for human weal, 

 Tinder-box, matches, fire-irons, flint and steel. 



We can give no further particulars of these early inven- 

 tions, but our readers may be interested in tracing the 

 lines of modern improvement. Old folks can remember 

 when " Any matches to-day ; buy my matches," were 

 common London cries, and the articles offered for sale were 

 strips of deal about six inches long and more than half an 

 inch wide. They were pointed at each end, and dipped in 

 melted brimstone. A piece of greasy rag well charred by 

 partial burning, constituted the tinder, usually kept in a 

 circular tin box with a cover that held a candle, and accom- 

 panied with pieces of black flint, and a steel implement like 

 a miniature hoe with a horizontal handle like a flat-iron. 

 This was held in the left hand, the flint struck smartly 

 against its edge, and a shower of sparks sent down 

 upon the tinder. The performer blew gently upon the 

 first portion that ignited, put the match to it, and set 

 the brimstone alight. A round tin damper was then 

 pressed upon the timber to put it out, and the operation 

 was finished. It was an easy one for most folks to learn, 

 but some clumsy hands boggled over it, and could elicit 

 neither spark nor flame. To this day some smokers use a 

 flint, and Amadou tinder, made of a fungus, Polyporus 

 fomentarius, beaten out and steeped in a solution of salt- 

 petre ; but few of these, or of the old operators in our 

 grandmother's kitchens ever knew that they were pro- 

 ducing objects well worth seeing under the microscope. 



* For a complete account of the theory of the method here con- 

 sidered, the mathematical reader should refer to Worms' admirable 

 treatise on " The Earth and its Mechanism," to which I have been 

 indebted for most of the above facts. It is worthy of notice that 

 in all the 1G6 experiments considered above, there was not a single 

 instance in which a ball fell either exactly below the point of sup- 

 port, or exactly where it should have fallen, according to theory. 

 We can very well understand this, of coarse, when we remember 

 the multitude of circumstances (individually minute, yet collectively 

 appreciable) which affect the progress of a falling body, let our pre- 

 cautions to ensure accuracy be what they may. It will be admitted 

 that the balls let fall in these experiments had a much better chance 

 of falling undisturbed than a ball fired in the open air from a gun 

 of any sort, fixed in a vertical position, could have of rising straight 

 to its highest point, and then falling straight down again. Yet the 

 paradoxist " Parallax " gravely assures his pupils that he once fired 

 forty balls from an air-gun tied in a vertical position, and that two 

 of these fell back into the muzzle of the gun. I would not be so 

 rude as to say with Dante, " lo non vidi, ne credo che sia ; " rather 

 would I imitate the politeness of the Frenchman, who, on a similar 

 narrative being related to him, said : "Aha! my good sir, thanks; 

 you have seen this, therefore I believe it. I would not have be- 

 lieved it had I seen it myself." For all I know to the contrary, 

 the similar narrative was " Parallax's" famous canal experiment. 



