The number of valuable substances which can be extracted from coal-tar is marvellous, and would surprise gas manufacturers of a generation ago, who gladly gave away the tar to any one who would take it. The last product of the black and ill-smelling fluid is a substance which has been named Saccharin, on account of its extreme sweetness, and the discovery is due to Professor Fahlberg. Saccharin is said to be two hundred and thirty times sweeter than the best cane-sugar. It has a great interest for the medical profession, for it can be used to render palatable the food of patients suffering from diabetes, and has been already adopted for this service in one of the Berlin hospitals. At present, the new sweetener costs forty shillings per pound. It has been ascertained by experiment that saccharin is innocuous; and we may feel sure that if its price can be reduced, it will become a formidable rival to sugar. The chief of the United States Geological Survey, Major Powell, has discovered near California what he believes to be the oldest human habitations on the American continent. The mountains in the vicinity are covered with beds of lava, in which have been excavated square rooms, lined with a kind of cement made with lava. Although these rock-dwellers were of prehistoric time, their work shows traces of an advanced civilisation. Several articles of pottery have been found in these cave-dwellings, as well as a kind of cloth made of woven hair. Wrapped in such a cloth, which tumbled into dust when touched, there was found a small image resembling a man. No fewer than sixty groups of these villages in the lava have been found. Mr Eric S. Bruce, who has been experimenting during the past year for the government with a balloon for signalling purposes, which he has invented, is about to exhibit a balloon of the same kind at the Crystal Palace, Sydenham. This aërostat will have a capacity of eighty thousand cubic feet, sufficient to give it the necessary lifting power to carry up several passengers. The balloon will be a captive one, like that exhibited at Paris in 1878, and will, like its huge forerunner, be hauled down to the earth after each ascent, by steam-power. It will ascend for the amusement of visitors during the daytime, telephonic communication being maintained between the car and the earth; while at night it will be illuminated by the electric light, so that Mr Bruce’s method of signalling may be fully demonstrated.