Hectolitre Hurter and Driffieid
Hectolitre (as above, and a pound). One hundred
litres. (See Weights and Measures.)
Hectometre (as above, anda measure). One hundred
metres. (See Weights and Measures.)
Heliography (as above, andI draw or write). Syn-
onymous with Photography.
Heliogravure (as above ; second syllable through the French). See Photogravure.
Heliostat (as above, anda fixed position or station).
An instrument consisting of a mirror driven by clockwork, for making the sun virtually stand still, as in observing or pho-tographing.
' Heliotype (as above, withan impression or print, as
of a seal). A collotype process of Mr. Ernest Edwards, in which a stripped pellicle is used as a printing surface. (See Collotype.)
Hermetic, or -al. According to the art of the Egyptian Hermes, the reputed first public teacher of the experimental sciences. The hermetic seal is the closing of a glass vessel by melting, as in the case of the ordinary tubes of chloride of gold.
High-Lights. The brightest parts of a picture, which are represented by the greatest density or opacity, in the negative, as the face in portraits, the sky and other bright portions in the landscape.
History of Photography. See Photography.
Hurter and Driffield, Method of. See Exposure, and