THE EFFECTS OF LIGHTNING. 



69 



phenomena at Drigg are conclusive as to the recency of the formation of the 

 fulgurites, and are therefore fatal to these hypotheses. 



The hillocks of sand in which the fulgurites at Drigg are formed are shifting, 

 being .subject to constant change by the wind. The tubes in them must, there- 

 fore, be of recent formation. 



But it is necessary to show that the state in which the sand is found in the 

 j internal and external coating of the tube, as well as in every part of its thick- 

 ness, can be produced by intense heat. 



This has accordingly been done. The sand in which the tubes have been 

 formed has been exposed to the action of various degrees of heat by means of 

 the blowpipe, and effects have been produced which correspond with the state 

 of the tubes, and prove that intense heat can produce the observed effects. 



Since we have in the electricity of the machines another lightning infinitely 

 less in its degree, but still the same in kind, a further corroboration of this hy- 

 pothesis would be obtained, if by means of this artificial lightning artificial ful- 

 gurites could be formed. MM. Savart, Hachette, and Beudant, transmitted the 

 charge of a powerful electrical battery through a mass of glass reduced to pow- 

 der, and obtained fulgurites an inch in length, and having an external diameter 

 varying from an eighth to a tenth of an inch, with an internal diameter of about 

 the twenty-fifth of an inch. 



One step more is necessary to establish the origin of fulgurites. This step 

 would consist in producing an example of the lightning being actually seen to 

 strike the ground where a fulgurite was afterward found, none having been 

 there before. This step is not wanting. 



Dr. Fiedler, who has published a work in German on fulgurites, supplies the 

 following facts : 



An apothecary of Ffederichdorf was brought to two men who had been 

 struck with lightning. He found in the ground where they lay two fulgurites, 

 like those of La Senne. 



On the confines of Holland, in a sandy country, a shepherd, after having 

 seen the lightning strike a hillock of sand, found in the very point where it 

 struck a fulgurite. 



On the 13th of July, 1823, lightning struck a birch-tree near the village of 

 Rauschen, in the province of Samlande, on the shores of the Baltic, and at the 

 same time set fire to a juniper-bush. The inhabitants ran to the spot, and found 

 near the tree two narrow and deep holes. One of them, notwithstanding the 

 cooling effect of the rain which was falling, was hot to the touch. Professor 

 Hagen, of Konigsberg, examined these holes, and found them, after excavation, 

 to have all the usual characters of fulgurites. 



The origin of fulgurites may then be considered as demonstrated. 



V. MECHANICAL EFFECTS. ^ 



The mechanical effects of lightning, seen in piercing solid bodies with holes, 

 in splitting them in pieces, and in projecting their fragments (sometimes of 

 enormous weight) to great distances, are so well known, and so generally ad- 

 mitted, that it will be needless to multiply instances in proof of it ; but a cir- 

 cumstantial statement of some remarkable cases of this kind may throw light 

 upon the manner i-n which the electric fluid acts. 



In the autumn of 1778 lightning struck the house of Casselli, an engineer, at 

 Alexandria. It did no damage, but pierced the panes of glass in the windows 

 with several small holes about the sixth of an inch in diameter. Small cracks 

 in the glass diverged from these holes as centres. 



In August, 1777, lightning struck the steeple of the parish church of St. 



