When a jar of oxygen is held over the neck of the retort generating the phosphuretted hydrogen, a bright flash of light and explosion are observed; and if the experiment is performed in a darkened room, it is just like a sudden flash of lightning. A bottle of chlorine held over the neck [Page 172] of the retort, and dipping of course in the water of the basin, produces a green flame every time the bubble of gas passes into it. That curious appearance of light, sometimes seen in marshy districts, called will-o'-the-wisp, is supposed to be due to the escape, from decomposing matter, of bubbles of hydrogen, nitrogen, &c., through which the spontaneously inflammable phosphide of hydrogen is diffused. At a place called Dead Man's Island, near Sheerness, magnificent effects of this kind are sometimes apparent when the mud banks are accidentally stirred at night by a boat-hook. A credible observer says, he once saw there a flash of yellowish-green light, accompanied with noise, about thirty feet in height. The apparent height might be due to the duration of the impression of the flash on the eye, as the light from the burning phosphuretted hydrogen ascended rapidly upwards. The source of this gas appears to be due to the fact, that during the time some Russian ships were watched by the Brest fleet, a number of the sailors died of cholera, and were buried in the banks; the decomposition of the bone containing phosphorus would account for the appearance of light already described. With the discussion of some of the most interesting properties of the thirteen non-metallic elements we take leave of the subject of chemistry, reserving the consideration of the metals for another popular juvenile work, of which they will form the subject. In answer to the oft-repeated question, "Where can I get the _things_ for the experiments?" it may be stated that every kind of glass vessel and the chemicals mentioned in this chapter, can be procured either of Messrs. Simpson, Maule, and Co., Kennington, or of Griffin and Co., Bunhill-row, or Bolton and Co., High Holborn. [Illustration: Fig. 158. Will-o'-the-wisp.] [Page 173] CHAPTER XIII. FRICTIONAL ELECTRICITY. [Illustration: Fig. 159. Franklin and his kite.]