SCIENTIFIC.

Saturday Advertiser, Volume III, Issue 124, 24 November 1877, Page 13

SCIENTIFIC.

SPECTRUM ANALYSIS.

The Times has just received an account of a proposed new method’ in solar spectrum analysis by Mr P. S. Langley, communicated to the meeting of the National Academy held in Washington. The attempts to determine the motion of a heavenly body along the line of sight by the altered wave length of its light have received a great deal of attention, and the possibility of obtaining reliable results by such a method have been often discussed. Mr Langley’s purpose is to show how the reality of the phenomena may be observed in another mode of investigation not liable to as many difficulties as in the case of the stars. This is the observation of the different wave lengths of light coming from the east and west limbs of the sun, which, owing to its rotation on its axis, have equatorial velocities that together make up nearly 2| miles a second. Although, this speed is insignificant when compared with the velocity of light, yet it has been found to produce the phenomena in question to an appreciable degree. The essential arrangements of the apparatus make provision for two pairs of right-angled prisms of total reflection so disposed in connection with a spectroscope, that the spectra can be formed side by side of light from different parts of the sun. The spectra are arranged so that one is of light coming from one edge of the sun, and the other from a point 180 degrees distant. The instruments being in adjustment if these points are in the neighbourhood of the solar poles which are relatively at rest, all the lines will be continuous on both spectra. But if the instrument is rotated till the light comes from points on the eastern and western sides of the sun, which are in relative motion, the solar lines will be discontinuous, . the one spectrum looking as if slid alongside the other. The theoretic amount of displacement is aboutone-lialf such as is capable of being measured by other existing instruments ; and Mr Langley in his communication expressed his conviction that this he should be able to measure with exactness with his instrument. He urged that instrumental error was impossible, as by this method solar and telluric lines are. alike affected. At the time of writing, his. instruments had not been long enough in his hands to do work.

THE WASTE OF COAL IN MODERN FIRE-PLACES. As winter is coming upon us this subject is of particular interest to all our readers. We, therefore, gladly insert the following communication from a correspondent of the Furniture Gazette, who writes :As the supply of coal is limited, and the consumption increasing, its economy is of prime importance. The waste in domestic fireplaces in the shape of smoke and misdirected heat varies from 50 to 80 per cent, in many cases, while the discomfort of smoky rooms, bad cookery, and draughts, drives many to seek in public-houses a costly alternative. It is well known that bottom-fed fires consume, while top-fed fires create smoke. The difficulty has long been how to feed domestic fires at the bottom. A slight alteration in the front bars is all that is necessary. If one or two of the lower bars are movable,'; the hot coal may be lifted up till the fire is replenished below. The bottom of the firebox could easily be covered with a piece of sheet-iron, to prevent slack coal from falling before it is consumed, and a" narrow slit or a damper would provide egress for the thoroughly-consumed ashes. A receptacle at the fire-back would utilize much of the heat wasted on bricks, and might be fitted with utensils for warm water, stewing,, &c., without a separate fire under the oven. Constant dropping wears away stones, and. constant waste in trifles means much in the long run.