950 



COPYING 



In the first analysis the proportion of tribasic phosphate of lime (bono-oarth) 

 reaches 54-89, and in the second analysis 57'12 per cent. 



Mineral deposits rich in phosphate of lime occur in the Bala Limestone at 

 Cwmgwymnen, about 16 miles from Oswestry ; but they do not appear to be of copro- 

 litic origin. They have been worked for agricultural purposes, and were described by 

 Dr. A. Voelcker before the British Association in 1865. 



Attention has recently been called to a remarkable phosphatic deposit in South 

 Carolina, which is now extensively worked. This deposit occurs in beds of post-pliocene 

 age, but is largely composed of nodules of altered marl derived from an Eocene rock 

 known as the great Carolinian Marl Bed. These nodular fragments from the mother- 

 rock are rich in organic remains, and are associated with bones and teeth of land 

 animals of more recent age. For a description of the deposit, see ' The Phosphate 

 Kocks of South Carolina,' by Francis S. Holmes, A.M. Charleston, 1870. Soo APATITE ; 

 MANUBE. 



COPYING. A new and important quality of writing-inks was introduced by the 

 indefatigable James Watt, in 1780, who in that year took out a patent for copying 

 letters and other written documents by pressure. The modus operandi was to have 

 mixed with the ink some saccharine or gummy matter, which should prevent its 

 entire absorption into the paper, and thus render the writing capable of having a copy 

 taken from it when pressed against a damp sheet of common tissue paper. But 

 although this process was very imperfect, the writing generally being much besmeared 

 by the damping, and the copies, in many cases, only capable of being read with great 

 difficulty, it was not for seventy-seven years after the invention of Watt that any 

 improvements in such inks were attempted. The firm of Underwood and Burt patented 

 a method of taking copies by the action of a chemically-prepared paper, in a chemical 

 ink, by which, not only are far superior copies taken, and the original not at all 

 damaged, but many copies may be taken at one time from a single document. Printed 

 matter may be also copied at the same time, on the same beautiful principle. Wo give 

 the specification of Mr. Underwood : 



' But while the means employed for producing the desired effects may be varied, 

 I prefer the following for general use : I damp the paper, parchment, or other mate- 

 rial which I desire to copy upon, with a solution of 200 grains of the yellow or neutral 

 chromate of potash dissolved in 1 gallon of distilled water, and either use it immedi- 

 ately, or dry it and subsequently damp it with water as it is required for use. I then 

 prepare the material which I use for producing the characters or marks, and which 

 may bo called copying ink, by simply dissolving (in a water-bath) pure extract of 

 logwood in distilled water ; or, for printing, I use a varnish or other similar material 

 soluble in water, and dust, or throw over it powdered extract of logwood. If I desire 

 to take twenty copies from an original, I use about six pounds of the pure extract of 

 logwood to a gallon of distilled water ; but a larger number of copies may be taken by 

 dusting or throwing over the original, before the ink has thoroughly dried, a powder 

 composed of five parts of powdered extract of logwood, one part of powdered gum 

 arabic, and one part of powdered tragacanth. When I desire to print from an original, 

 in producing which I have used ink prepared as before described, I proceed by damping 

 six sheets of paper, prepared as before described, and having taken off all superfluous 

 moisture with good blotting paper, I place the original upon the upper sheet and press 

 the whole for about half a minute in a copying press ; I then remove the original, and 

 in its place put six other sheets of the prepared paper in a damp state, and subject 



