November 1, 1888.] 



♦ KNOW^LEDGE ♦ 



11 



able to suppose that a child who had but lately learned the 

 nature of numbers, and was altogether unacquainted with 

 the ordinary properties, should have intuitively recognised 

 abstruser properties. A more natiu'al explanation must 

 burely exist, if we consider the matter attentively. 



It happens that I am able, from my own experience, to 

 advance an explanation which accords well with the facts, 

 and especially with the circumstance that calculating boys 

 usually lose their exceptional power of rapid reckoning 

 when they are instructed in and taught to practise the 

 ordinary methods; for I used formerly to possess, though 

 in a slight degree only, a power of finding divisors, products, 

 and so on, which — unlike ordinar// skill in calculation — 

 required only to be expanded to efl'ect what Colburn efiected. 

 It was, in point of fact, simply the power of picturing a 

 number (not the written number, but so many " things "), 

 and changes in the number, corresponding to division or 

 multiplication as the case might he. Thus the number 24 

 would be presented as two columns of dots each containing 

 ten, and one column containing four on the right of the 

 columns often. If this number were to be multiplied by three, 

 all that was necessary was to picture three sets of dots like 

 that just described ; then to conceive the imperfect columns 

 brought together on the right, giving six columns of ten 

 and three columns each of four dots ; and these three gave 

 at once (by heaping them up properly) another column of 

 ten with two over : in all seven columns of ten and one 

 column of two — that is, seventy-two. This takes long in 

 writing, but, as pictured in the mind's eye, the three sets 

 representing 24 formed themselves into the single set repre- 

 senting 72 in the twinkling of an eye (if the mind's eye can 

 be imagined twinkling). The process for division was not 

 exactly the reverse of that for multiplication. Thus, 72 

 being pictured as seven columns of ten and one of two, to 

 divide it by 8, the first six columns of ten were pictured as 

 giving twenty sets of three horizontal dots ; the next column 

 of ten gave three vertical triplets, counted from the top ; 

 and then the remaining dot at the bottom, with the other 

 two in the imperfect column gave another triplet, or twenty- 

 four triplets in all. These triplets could all be sei-n as it were; 

 and the only mental calculation, properly so called, consisted 

 in counting them, which of course was e;isy, twenty of them 

 being as it were already numbered. 



R. A. Proctor. 

 {To be continued.) 



DANGER FROM LIGHTNING. 



aSt j a!* i 1 1 EIIE are persons not otherwise wanting in 

 courage who experience an oppressive sense 

 of terror when electrical phenomena are in 

 progress. The Emperor Augustus used to 

 suH'er the most distressing emotions during 

 a thunderstorm, and ho was in the habit of 

 retiring to a low vaulted chamber under- 

 ground, unilor the mistaken notion that lightning never 

 penetrates far below the earth's surface. Major Yokes, the 

 Irish ])oli(0 ollicer — a man whose daring was proverbial — • 

 used to be ])rostrated by terror during a thunderstorm. We 

 cannot doubt that, in these instances, nervous effects are 

 produced which are wholly distinct from the fear engendered 

 by the simple consciousness of danger. 



We have said that the danger is small when a thunder- 

 storm is ill progress. If we consider the number of persons 

 exposed during a year, in England, to the eftects of light- 

 ning-storms raging in their immediate neighbourhood, and 

 compare with that number the small number of recorded 



deaths, we shall see that the prohahility of being struck by 

 lightning is very small indeed. The danger we are exposed to 

 in travelling along the most carefully regulated railway is 

 many times gi-eater than that to which, under ordinary 

 circumstances, we are expo.sed when a thunderstorm is 

 raging around us. Yet, in cases of this sort, men do not 

 reason according to the doctrine of chances — nor, indeed, is 

 it desirable that they should. There are measures of pre- 

 caution which, small though the danger may be, it is well to 

 adopt. In a railway carriage, it would be foolish to let the 

 mind dwell upon the danger to which we are in reality 

 exposed, since we can do nothing towards diminishing it. 

 But it would be as unreasonable to neglect precautions in 

 the presence of a heavy thunderstorm, merely because the 

 danger of being struck is small, as it would be to neglect 

 the rules which regulate powder-stores, merely because the 

 instances in which fires have been caused by carrying cigar- 

 lights in the coat-pocket, or by wearing ii'on on the sole of 

 the boot, are few and far between. 



We have mentioned one precautionary measure adopted 

 by the ancients. The notion that lightning does not pene- 

 trate the earth to any considerable depth was in ancient 

 times a widespread one. It is still prevalent in China and 

 Japan. The emperors of Japan, according to Krempfer, 

 retire during thunderstorms into a grotto, over which a 

 cistern of water has been placed. The water may be 

 designed to extinguish fire produced by the lightning ; but 

 more probably it is intended as an additional protection 

 from electrical effects. Water is so excellent a conductor of 

 electricity that, under certain circumstances, a sheet of 

 water affords almost complete protection to whatever may 

 be below ; but this does not prevent fish from being killed 

 by lightning, as Arago iias pointed out. In the year 1670, 

 lightning fell on the lake of Zirknitz, and killed all the fish 

 in it, so that the inhabitants of the neighliourhood were 

 enabled to fill twenty-eight airts with the dead fish found 

 floating on the surface of the lake. That mere depth is no 

 jirotection is well shown by the fact of those singular 

 vitreous tubes called fulgurites, which are known to be 

 caused by the action of lightning, often penetrating the 

 ground to a depth of 30 or 40 feet. And instances have 

 been known in which lightning has ascended from the 

 ground to the storm-cloud, instead of following the reverse 

 course. From what depth ■ these ascending lightnings 

 spring it is impossible to say. 



Still, we can scarcely doubt that a place underground, 

 or near the ground, is somewhat safer than a place several 

 storeys above the ground floor. 



Another remarkable opinion of the ancients was the 

 belief that the skins of seals or of snakes afford protection 

 against lightning. The Emperor -\ugustus, before men- 

 tioned, used to wear seal-skin dresses, under the impression 

 that he derived s;ifety from them. Seal-skin tents were 

 .also used by the Romans as a refuge for timid persons 

 during severe thunderstorms. In the Cevennes, Arago 

 tells us, the shepherds are still in the habit of collecting the 

 cast-off' skins of snakes. Tiiey twist them round their hats, 

 iinder the belief that they thereby secure themselves against 

 the effects of lightning. 



Whether there is any v&xl ground for this belief in the 

 protecting efl'ects due to seal-skins and snake-skins is not 

 known ; l)ut there can be no doubt that the material and 

 cokmr of clothing are not without their importance. When 

 the church of Chiiteauneuf-les-Moutiors was struck by 

 lightning during divine service, two of the officiating priests 

 were severely injured, while a third escaped — who alone 

 wore vestments ornamented with silk. In the s:ime 

 explosion nine peiisons were killed, and upwanls of eighty 

 injured. But it is noteworthy that several dogs were 



