Sept. 22, 1855.] 



THE GARDENERS' CHRONICLE. 



C31 



M. Arago is 



tedd^Tplants that are established in the same place, 

 after all danger of such severe frost is over as would 

 be likely to penetrate through the glass. Last year I 

 gardened off 5000 bedding plants in this way. Orchard- 

 houses are also first-rate places for protecting winter 

 salads in after the plants are dried off and put to rest — 

 they then occupy but little space. /. Daniels, Gardener, 

 Swyncombe House, Henley-on-Thames. 



Sottas; of SSoofcg. 



— ♦ — 



Meteorological Essays. By Francois Arago. With an 

 Introduction by Baron A. von Humboldt. Translated 

 under the superintendence of Colonel Sabine, R.A. 

 Longmans. 8vo, pp. 504. 



In this insular variable climate the weather is the great 

 subject of everybody's attention ; and all works relating 

 to it are welcome to the English public. Will it be 

 fine ? Will it cease raining \ What sort of weather 

 shall we have to-morrow % Can we reckon upon a 

 Queen's day ? Is the next month likely to be fair or 

 stormy % These and a hundred similar inquiries are 

 heard everywhere, and are constantly repeated ; for no 

 one knows with certainty how to answer them. A work 

 then by such a man as Arago, although relating to only 

 a small portion of the weather subject, will be read with 

 interest as well as with the respect due to so great a 



Same. 



More than half the volume before us is occupied by 

 thunder and lightning. About another hundred pages 

 treat of the aurora borealis, and the remainder relates 

 to electro-magnetism, animal electricity, and terrestrial 

 magnetism. Each of these questions is illustrated by a 

 crowd of facts patiently gathered from an infinite multi- 

 tude of sources, and constituting a set of data with 

 which all theories must be reconcileable if true. Many 

 of the relations are extremely curious, while all are 

 made to have a direct bearing upon the points they are 

 intended to elucidate. 



Our scanty space forbids our doing more than con- 

 cisely touching upon some of the questions discussed in 

 that division of the work which is assigned to thunder 

 and lightning. It is a disputed point whether lightning 

 occurs without thunder or the reverse. 

 Bcarcely able to answer these questions. 



"The phenomenon of lightnings without thunder, 

 with a perfectly clear sky, is too well known, and rests 

 on too general experience for it to be necessary for me 

 to cite on this point the testimony of any particular 

 meteorologist. Who, indeed, in our climates has not 

 Seen and remarked ' heat-lightnings f Bergman tells 

 us that in Sweden, where they are also very common, 

 the peasants call them ' Barley lightnings' (korn-bleck), 

 because they are usually seen in August, when the 

 Barley is beginning to ripen. 



m It is by mistake that it has been asserted that heat- 

 lightnings always remain near the horizon. Their light 

 sometimes overspreads the whole visible extent of the 

 heavens. This remark will not be without its use when 

 ye come to inquire whether heat-lightnings have an 

 independent existence, or are only the reflection of 

 other lightnings. 



" Seneca asserted that thunder sometimes takes place 

 without lightning. (Qucest. Nat lib. ii. § 18.) 



* I am ashamed to have to confess that as respects 

 Europe I am almost reduced to Seneca's statement. 

 Thunders without lightning, notwithstanding the points 

 of theory on which they might afford solutions, have 

 but little excited the attention of observers. The cita- 

 tions which I am enabled to make from other parts of 

 the world leave, 1 think, little room to doubt the reality 

 Mid generality of the phenomenon. 



"Thibaultde Chanvalon wrote in Octoher, 1751, in 

 bis register of meteorological observations at Marti- 

 nique : — « Of eight days in this month on which it 

 thundered there were two days without lightning. 9 In 

 November, I read : — < Thunder only on one day ; three 

 rather strong thunderclaps, but without lightning? 



"On the 19th March, 1768, near Cosseir, in the Red 

 Sea, a violent thunder-clap spread consternation among 

 the crew of the small bark on which the traveller James 

 Bruce was proceeding. This thunder-clap had not been 

 preceded by any lightning:' 



The precautions which may be adopted by persons 

 afraid of lightning are described as follows : — 



Franklin has given some precepts for the use of 

 ^ch persons who, during thunderstorms, are in houses 

 &<rt provided with lightning conductors. 



w H® recommends them to avoid the neighbourhood 



?u .~P* aceSt Lightning does indeed often enter by 



*ne chimney, on account of the internal coating of soot, 



^hich is one of the bodies for which, as for metals, 



8 {fjmfr evinces a preference. 



*or the same reason avoid, as much as possible, 

 petals, gildings, and mirrors, on account of their 

 quicksilver. 



i a e ^ ea * P^ ace * 9 tne middle of the room ; unless, 

 <teed, there should be a lamp or chandelier hanging 

 from the ceiling. 



1 " T J*e less the contact with the walls or the floor, the 



s the danger. A hammock suspended by silken 



?*as m tne middle of a large room would be the safest 



beat^i * D . tne a °sence of means of suspension, the next 



suh e * 8 0n SUDstances which are bad conductors, 



cu as glass, pitch, or several mattresses, 

 oth . ordin 8 to Nollet, with similar elevations, and all 

 With* 1 circumstaacea equal, spires and steeples covered 



bv 1* h^ are more often and more v™ 1 ^^ struck 

 / "gotning than those which are built of stone. 



" I do not think that tbe cause of such a difference 

 should be sought in some specific difference between the 

 substance of the slate and that of the stone. It would 

 be more likely to be found in the humidity which, during 

 heavy rain, so easily penetrates between the slates to 

 the timber and laths on which they rest, and to the 

 number of iron nails employed in fixing them. 



" The greater the mass and the volume of the conduct- 

 ing matter brought together in one place, the greater 

 the chance of being struck by lightning in its neighbour- 

 hood. This being once admitted, since living man is a 

 sufficiently good conductor of the fulminating matter, 

 ought we utterly to reject the opinion of some able 

 physicists (of Nollet, for example), who think that the 

 danger of being struck by lightning in a church increases 

 with the number of persons assembled there. 



" There is another cause which may contribute to 

 render numerous assemblages of men or animals dange- 

 rous during thunder-storms. Their perspiration cannot 

 fail to occasion an ascending column of vapour ; and, as 

 it is well known that moist air is a better conductor of 

 lightning than dry air, such a column has a natural 

 tendency to attract the lightning by preference to the 

 place from which it proceeds. Need we therefore be 

 surprised that flocks of sheep are so often struck by 

 lightning, and that a single stroke should sometimes 

 cause the death of 30, 40, and even 50 of those animals? 



u In America it is a generally received opinion, that 

 barns full of grain or of forage are more often struck by 

 lightning than other buildings. 



" This circumstance would also seem to be attributable 

 to an ascending current of moist air, of which the origin 

 maybe easily accounted for, since crops are usually 

 housed before they have arrived at a state of great 

 dryness. 



" It sometimes happens that one person in the midst 

 of a numerous group is struck by lightning, without the 

 determining causes of this kind of selection being at all 

 discerned, — without the sufferer wearing more metal 

 about his person than the rest of the party, and without 

 his position relatively to surrounding objects presenting 

 any apparent peculiarity. 



■ I say any apparent peculiarity, because a cause may 

 be active without being apparent ; for a mass of iron 

 concealed in the thickness of a wall produces just as 

 much effect as if it was uncovered, &c. It can very 

 rarely happen that it can be safely affirmed, that all 

 circumstances were identically the same in the situations 

 occupied by the persons struck and those who were 

 spared. The latter may have been further from some 

 mass of metal, water, &c, existing, concealed and un- 

 suspected, under the floor, behind a wainscot, in the 

 earth, &c. 



* It would seem difficult to arrive, in this manner, at 

 discovering whether there are any specific differences 

 between different individuals in their degree of liability 

 to being struck. This doubt could only be elucidated 

 by the aid of indirect experiments, which will be ex- 

 amined in a future chapter. In this place I content 

 myself with saying that there are specific differences ; 

 and that, during a thunder-storm, in situations perfectly 

 similar, one man may, by the nature of his constitution, 

 be in greater danger than another.*" 



Differences of opinion still exist here and there as to 

 the true value of lightning conductors. From very 

 early times it has been believed that the effects of light- 

 ning might be averted. 



"Herodotus (book iv. chap 94), relates, that when it 

 thunders and lightens the Thracians are in the habit of 

 shooting arrows against the sky, to threaten it. 

 Remark that he distinctly says ' to threaten it.' 

 There is no question at all of the power which the 

 arrow, being metallic and pointed, would have of taking 



from the clouds some little portion of their fulminating 

 matter. This is so clear, that even the fanatically- 

 ardent admirer of antiquity, Dutens, drew back from 

 the idea of assimilating the Thracian arrows to the 

 lightning-conductors of modern times, and from making 

 the invention of Franklin's apparatus go back to the 

 time of Herodotus." 



" In the 15th century, a naked sword was placed at 

 the mast-head of ships to turn aside lightning from 

 them. St. Bernardino of Sienna, who has been the 

 means of transmitting the knowledge of this custom, 

 speaks of it as a prejudice. ( Laboissiere, Academie du 

 Gard, 1822.)" 



" Ctesias of Cnidos, one of the companions of Xeno- 

 phon, relates, in a passage which has been preserved to 

 us by Photius, that he had received two swords, one 

 from the hands of Parisatis, mother of Artaxerxes, the 



* " The matter which darts in sparks from the conductor of an 

 electric machine after the plate has been turned for some time, 

 is fulminating matter. Like fulminating matter, or lightning, it 

 is transmitted almost without loss of power through great 

 extents of metal, water, &c. It also traverses pretty freely a 

 number of men joined hand in hand, and forming a chain. It 

 is, however, found that there are some persons who abruptly 

 arrest, or even form an obstacle to, the communication, and who 

 do not feel the shock, even if placed next to the first person in 

 the file. Such exceptional persons must be classed exceptionally 

 among the non-conducting or imperfectly-conducting bodies 

 which lightning respects, or at least rarely strikes. 



u Such strongly marked differences imply intermediate shades. 

 Now every degree of conductibility corresponds during a thunder- 

 storm to a certain degree of danger. A man, who should be as 

 good a conductor as a metal, would be as liable to be struck as a 

 mass of metal ; a man who would interrupt the transmission of 

 electricity when forming one of a chain, would be almost as littl 

 likely to be struck as if his bodv were of the nature of glass or o 

 resin. Between two such extreme cases there would be person 

 whose liability would be similar to that of wood, of stones, &c. 

 Thus it would seem that the place occupied by each person is not 

 the only influential circumstance: the physical constitution of 

 the individual may also have some share in the result;' 



» >i 



other from those of the king himself ; he adds : — * If 

 these 6words are plaited in the ground with the point 

 uppermost, they drive away clouds, hail, and thunder- 

 storms. The king,' he goes on to say, 6 made the expe- 

 riment in my presence, at his risk and peril. 



" In the time of Charlemagne, it was usual to put up 

 long poles in the fields to drive away hail and thunder- 

 storms ; but lest fanatical admirers of old times should 

 see in this practice an anticipation of Franklin's light- 

 ning conductors, I hasten to add that the poles were not 

 to be efficacious unless they were surmounted by pieces 

 of paper. Such papers or parchments were no doubt 

 covered with magic characters, since Charlemai^ne in 

 proscribing this practice, in a capitulary of 789, 

 described it as superstitious." 



At last we have the experiment- of Sir Snow Harris 

 and others which have ended in the present system of 

 trusting to sharp-pointed metallic rods as certain means 

 of attracting and nullifying the action of lightning. The 

 explanation of this is given by Arago with admirable 

 clearness and conciseness. 



n All other circumstances being equal, lightning 

 directs itself, generally speaking, by preference to the 

 most elevated portions of edifices. It is there, conse- 

 quently, that the preservative meaus, whatever they 

 may be, should be applied. 



"All other ciicumstances being equal, lightning 

 directs itself by preference to metals. When, therefore, 

 a metallic mass occupies the most elevated point of a 

 house, we may feel pretty nearly certain that lightning, 

 if it falls, will strike that point. 



" Lightning which has entered a metallic mass only 

 does mischief to surrounding masses at the moment 

 when it quits the metal, and in the vicinity of the point 

 or points at which it issues from it. A house may, 

 therefore, be rendered safe from its highest point to its 

 foundations, if the metallic parts of the roof are pro- 

 longed without interruption to the ground. 



" Damp earth offers to the fulminating matter which 

 is passing along a metallic bar a channel by which it 

 escapes easily and without effort, without detonation, 

 and without producing any kind of damage, providing 

 the bar plunges a little deeply into the earth. By 

 carrying the continuous bar which has already pre- 

 served from injury the exterior of a building down some 

 way into the ground, which is always damp, the founda- 

 tion, and, speakiug generally, the whole subterranean 

 portion of the building will be similarly preserved." 



In like manner he deals with paragreles or apparatus 

 for averting hail. 



"The formation of hail appears to be indisputably 

 connected with the presence of an abundant quantity of 

 fulminating matter in the clouds. Withdraw that 

 matter, and the hail will either not be formed, or will 

 remain in its rudimentary state, so that all that falls 

 will be a harmless, extremely minute hail or sleet. 

 Does any one doubt the great benefit which, in some 

 countries, agriculture would receive from the disappear- 

 ance of hailstorms ? I reply, that in 1764 an enlight- 

 ened inhabitant of the south of France wrote in the 

 ' Encyclopedia,' * There is hardly ever a year in which 

 hail does not ravage the half, and sometimes three- 

 quarters, of the dioceses of Rieux, Comminges, Con- 

 serans, Auch, and Lomberi? The single storm of the 

 13th of July, 1788, smote in France 1039 communes. 

 An official inquiry made the damage amount to 25 

 millions of francs (one million sterling)." 



Instead of kites or other contrivances of that kind 

 Arago makes a very different though analogous sug- 

 gestion. 



" What I would wish is, that captive balloons should 

 be resorted to for this great and important experiment. 

 I should wish them to be seut up to a much greater 

 height than that attained by Romas's kites. If by 

 rising 300 or 400 feet above the elevations ordinarily 

 reached by the upper extremities of the rods of light- 

 ning conductors, there were obtained, instead of little 

 plumes or tips of flame, flames 10 or 12 feet long, what 

 may we not expect would happen when the whole 

 apparatus, having risen to a height three, four, or ten 

 times as great, according to circumstances, would almost 

 graze the under surface of the clouds I and when, more- 

 over (and this is an important particular), the metallic 

 point which is to attract the fulminating matter, and 

 which would be in communication with the long semi- 

 metallic cord which officiates as conductor, being fixed on 

 the upper part of the balloon, is presented to the clouds 

 nearly vertically, or in the position of the rod of an 

 ordinary lightning conductor ? It does not appear to 

 me that there would be anything too bold in supposing 

 that it might be possible to dissipate the most violent 

 thunder or hail storms by such means. At ail events, 

 an experiment so highly and directly interesting both to 

 science and to the agricultural wealth of countries is 

 well deserving of trial. If balloons of moderate dimen- 

 sions were employed, the expense would certainly be 

 less than the Vine-growing districts now expend use- 

 lessly in firing so many guns and mortars." 



Our last extract must be that which relates to the 

 organs which are most usually affected in deaths or in- 

 juries occasioned by strokes of lightning. 



w John Hunter said, that lightning in traversing the 

 body produces an entire and instantaneous destruction 

 of the vital principles. I must be pardoned for saying 

 that this is but repeating known facts in obscure terms. 

 According to Brodie, death follows from the action of 

 the lightning matter on the head. 



66 Edwards considered death caused by lightning to be 

 the result of a disorganisation of the nervous system. 

 Others confine the action to the cerebro-spinal system, 



