The block which gives the impression is always accurately brought down to the same place by means of a hinge; this spot is covered by a piece of thin leather stretched over it; the block is now inked, and being brought down to its place, gives an impression of the pattern to the leather: it is then turned back; and being inked a second time, the paper intended to be printed is placed upon the leather, when the block again descending, the upper surface of the paper is printed from the block, and its undersurface takes up the impression from the leather.
"On the Economy of Machinery and Manufactures"
Charles Babbage
They appear late in March, being green above, with an undersurface which is white, and cottony.
"Herbal Simples Approved for Modern Uses of Cure"
William Thomas Fernie