ERIOMETER

(Yunanca köken — orijinale bakınız.) An optical instrument proposed by the late Dr. Young for measuring the diameters of minute particles and fibres, by ascertaining the diameter of any one of the series of coloured rings they produce. " The eriometer is formed of a piece of card or a plate of bra , having an aperture of about a fiftieth of an inch in diameter in the centre of a circle about half an inch in diameter, and perforated with about eight small holes. The fibres or particles to be measured are fixed in a slider; and the eriometer being placed before a strong light, and the eye a isted by a lens applied behind the small hole, the rings of colours will be seen. The slider must then be drawn out or pushed till the limit of the first red and green ring (the one selected by Dr. Young) coincides with the circle of perforations, and the index will then show on the scale the size of the particles or fibres." (Brewster's Optics, Cabinet Cyclopcsdia.) [s. 427]