On July 28, 1885, at Luchon, on the Bigorre road a passer-by saw lightning fall twenty yards away from him. Recovered from the shock, he went out of curiosity to look at the result, and saw the wall at the edge of the road, the schistous and chalky rocks, even the trees themselves, coated over with layers of brown. It was certainly a case of the lightning having effected a deposit. This latter was very curious. Lines could be traced on it with the finger-nail, it fell to powder under slight pressure, became soft with gentle rubbing, caught fire from a candle, and then gave off a resinous odour with much smoke. What is this resinous matter? That is what no one yet can say. In the month of July, 1885, on the day following a violent thunderstorm which had struck the telegraph-office in the station of Savigny-sur-Orge, I myself picked up a little black powder off the telegraph poles, which had been left by the lightning, and which had a sulphurous smell. The production of this ponderable matter has often been attributed to bolides, but direct observation proves beyond a doubt that the electricity carries various solid substances found on earth after a storm. Lightning is truly the most venerable of glass-makers. Long before the most remote peoples of antiquity appeared, whose glasswares encrusted with marvellous iridescent tones by the passing of the centuries, are unearthed by scientific excavations, and displayed in national collections; long before man could have learnt to make use of the resources of nature, lightning, burrowing in the sand, there fashioned tubes of glass that hold the hues of the opal, and are called fulgurites. The ancients seem to have known of these fulgurite tubes, but we owe the first precise description and the first specimen of these extraordinary vitrifactions to Hermann, a pastor at Massel in Silesia. His fulgurite, found in 1711, is in the Dresden Museum. Since this discovery, fulgurites have often been sought for and found. The tubes, contracted at one end, and ending in a point, are to be seen in sandy soils. Their diameter varies from 1 to 90 millimetres, and the thickness of their sides from half to 24 millimetres. As to the length, it sometimes exceeds 6 metres. Vitrified inside, they are covered outside with grains of sand agglutinated and apparently rounded as if they had been subjected to a beginning of fusion. The colour depends on the nature of the sand in which they have been formed. Where the sand is ferruginous the fulgurite takes a yellowish hue, but if the sand is very clean, it is almost colourless or even white. As a rule, the fulgurites penetrate the ground vertically, Nevertheless, they have been found in an oblique position. At times, also, they are sinuous, twisted, or even zigzag if they have met with pebbles of considerable size.