temperature, as this involves frequent renewal of pyramids already melted. These appliances are sold under the name of Seger “cones,” the latter word being evidently a misnomer. =Watkin’s Heat Recorder.=—This arrangement consists of a small block of fireclay, having a number of cylindrical holes in its upper face. Pellets of materials of progressive melting points are placed in the holes, in which they fit loosely. The block is placed in the furnace, and afterwards withdrawn and examined, when those which have completely melted will be seen to have sunk, and to possess a concave surface; others which have been superficially fused, will show rounded edges, whilst others will be intact. The melting point of the highest member of the series which is observed to have rounded edges is taken as the temperature of the furnace. The materials used in the manufacture of the pellets are approximately the same as those employed by Seger, being the same in number (60), and differing progressively by similar intervals. It is not evident that the method of observation is superior to the use of pyramids, although some workers may prefer it, and the arrangement is merely an alternative plan of using the Seger compositions. Watkin has also introduced a modification in which straight bars of clay compositions are supported at the edges, the temperature being deduced by observing which numbers melt, droop, or remain intact. =“Sentinel” Pyrometers.=—Under this name, Brearley, of Sheffield, has introduced a number of compositions, chiefly of salts, which possess definite melting points. These are made in the shape of cylinders, about 1 inch long and ¾ inch in diameter, which collapse completely when the melting point is attained. Compositions have been found which melt at certain temperatures known to give the best results in the treatment of different kinds of steel, and a cylinder of correct melting point, placed in the furnace on a small dish near to the steel, furnishes a simple and correct clue to the attainment of the desired temperature. The existing condition of a furnace may be discovered by taking a number of cylinders, having progressive melting points, and making observations after the manner described under the heading of Seger pyramids. A few “Sentinel” cylinders are frequently of use in the workshop or laboratory for other purposes, such as a rapid check of a given temperature in confirmation of the reading of an indicating pyrometer, or in discovering whether a certain temperature has been exceeded in a given case. “Sentinel” cylinders have been used in such a manner as to give audible warning of the attainment of a given temperature by means of a metal rod, which is made to rest on the cylinder, and which, when the cylinder melts, falls and completes the circuit of an electric bell. The upper range attainable by the use of ordinary metallic salts is not so great as in the case of silicates, but up to 1100° C.