WHITE, one of the colours of bodies. Though white cannot properly be said to be one colour, but rather a composition of all the colours together ; for Newton has demonstrated, that bodies only appear white by reflecting all the kinds of colour ed rays alike; and that even the light of the sun is only white, because it consists of all colours mixed together.
This may be shown mechanically in following manner Take seven parcels of coloured fine powders, the same as the primary colours of the rainbow, taking such quantities of these as shall be pro portional to the respective breadths of these colours in the rainbow, which are of red 45 parts, orange 27, yellow 48, green 60, blue 60, indigo 40, and of violet 80 ; then mix intimately together these seven parcels of powders, and the mixture will be a whitish colour : and this is only simi lar to the uniting the prismatic colours together again, to form a white ray or pencil of light of the whole of them. The same thing is done conveniently thus : Let the flat upper surface of a top be divided into 360 equal parts, all around its edge ; then divide the same surfice into seven sectors, in the proportion of the numbers above, by seven radii or lines drawn from the centre,. next let the respective colours be painted in a lively manner on these spaces, but so as the edge of each colour may be made nearly like the colour next adjoining, that the separation may not be well distinguished by the eye ; then if the top be made to spin, the colours will thus seem to be mixed all together, and the whole surface will appear of a uniform whiteness : and if a large round black spot be painted in the middle, so as there may be only a broad flat ring of colours around it, the experiment will succeed the better.
White bodies are found to take heat slower than black ones; because the lat ter absorb or imbibe rays of all kinds and Colours, and the former reflect them, Hence it is that black paper is sooner in flamed by a burning-glass, than white ; and hence also, black clothes, hung up in the sun by the dyers, dry sooner than white ones.
Will l'EHURST, (JOHN,) in biogra phy, an ingenious English philosopher, was born at Congleton, in the county of Cheshire, the 10th of April, 1713, being the son of a clock and watch-maker there.
On his quitting school, where it seems the education he received was very de fective, he was bred by his hither to his awn profession, in which he soon gave hopes of his future eminence.
At about the age of twenty-one, his eagerness after new ideas carried him to Dublin, having heard of an ingenious piece of mechanism in that city, being a clock with certain curious appendages, which he was very desirous of' seeing, and no less so of conversing with the ma ker. On his arrival, however, he could neither procure a sight of the former, nor draw the least hint from the latter con. cerning it. Thus disappointed, he fell upon an expedient for accomplishing his design ; and accordingly took up his resi dence in the house of the mechanic, pay ing the more liberally for his board, as he had hopes from thence of more readily obtainiwthe indulgence wished for. He was accommodated with a room directly over that hi which the favourite piece was kept carefully locked up ; and he had not long to wait for his gratification : fi,r the artist, while one day employed in examing his machine, was suddenly call ed down stairs ; which the young enqui. rer happening to overhear, softly slipped into the room, inspected the machine, and presently satisfying himself as to the se cret, escaped undiscovered to his own apartment. His end thus compassed, he shortly after bid the artist farewell, and returned to his father in England.
About two or three years after his re turn from Ireland, he left Congleton, and entered into business for himself at Derby, where he soon got into great employment, and distinguished himself' very much by se veral ingenious pieces of mechanism, both in his own regular line of business, and in various other respects, as in the construction of curious thermometers, barometers, and other philosophical in struments, as well as in ingenious contri vances fur water-works, and the erection of various larger machines : being con sulted in almost all the undertakings in Derbyshire, and in the neighbouring counties, where the aid of superior skill in mechanics, pneumatics, and hydrau lics, was requisite.