Mr Coret has invented what he calls a self-acting thermo-signal which by ringing a bell makes known to all within hearing when an axle or any other part of an engine is over-heated. It is a small brass cylinder, containing a system of flexible metal disks, and a dilatable liquid, which is to be fixed to the part liable to over-heating. While all goes well the instrument makes no sign; but as the temperature rises the liquid dilates, forces out a small metal pin at the end of the cylinder, which, as the wheel revolves, strikes a bell, and thereby warns the attendants. Thus the necessity for constantly watching an indicator is avoided.
Other subjects brought before the same Society are—A description of a chimney which does not occasion loss of heat, by Mr Toulet, 38 Avenue de l’Observatoire, Paris—Specimens of harmless colours which may be used with varnish, oil, or water, and are described as durable and remarkably brilliant. They are available for many purposes of decoration, but are specially intended, as they contain no poisonous element, for the colouring of children’s toys. These new colours are derived from the substances known to chemists as eosin and fluorescin—And certain manufacturers who have carefully studied the material give an account of the capabilities of jute, from which we gather that by proper preparation of the yarns, remarkable effects of colour, of mottling, of light and shade, and also a velvety appearance can be produced. The process is described as very simple and moderate in cost; so that applications of jute to decorative purposes hitherto not thought of may ere long become available.
It has been found by experiment that aniline black can be made to yield different colours: treated in one way it is a light violet, in another way it is a bluish pink, and in a third way it becomes blue.
Pure butter, as is stated in the _Journal_ of the Chemical Society, contains from ninety to ninety-eight per cent. of pure butter fat and a small quantity of water. Its colour should be from yellowish white to reddish yellow, but this depends on the kind of fodder given to the cows, and may be produced by means of beetroot or other plants possessed of colouring properties. The colouring matter may be detected by treating the butter with strong alcohol. The melting-point of pure butter is from thirty to thirty-seven degrees, while artificial butter melts at from twenty-seven to thirty-one degrees. Substances used to increase the bulk and weight of butter are chalk, gypsum, oxide of zinc, starch, and so forth. These neither improve its flavour nor its wholesomeness. The agreeable smell of pure butter, with a slight suggestion of milk, is not easy to imitate by artificial means.