io6 A Safety Paper for Cheques. [February, 
up our cheque with any ordinary writing ink, and pay it 
away in perfect confidence. Let us suppose it falls into bad 
hands. To discharge the writing he applies, say, a dilute 
acid or the solution of an acid salt. Immediately the whole 
surface of the cheque assumes one uniform red colour and 
the letters, lines, and other devices disappear. Suppose he 
then tries to undo the mischief by the application of an 
alkali or the solution of an alkaline salt. At once the whole 
document is turned blue, and the words, &c., are not repro- 
duced. If he applies the alkaline liquid first, the design is 
equally destroyed. Let us even suppose that the forger dis- 
covered some perfectly neutral liquid capable of removing 
writing ink. Even here he could be met by the simple 
contrivance of printing the design in a deeper or a paler red, 
produced by the application of a stronger or a weaker acid. 
If a design thus produced is moistened even with a neutral 
liquid, its distinctive shades will be affeCted and the cha- 
racters blurred. The invention further proposes to print 
inscriptions and marks on cheques partly by the method 
already described, and partly in ordinary printers’ ink, “the 
inks being so printed that the marks or inscriptions are com- 
posed of fine lines or lettering of the dye alternating with 
lines or lettering of printers’ ink, the printing being effected 
in a machine of very delicate registration.” Hence, if all the 
coloured part of the inscription is removed from a cheque, 
it is practically impossible to reprint it, even with the block 
with which such coloured part was originally produced. 
The acid which the inventor prefers is the oxalic, as it 
possesses the property of not corroding the plates or blocks 
used in printing. It forms upon the face of the plate a 
thin layer of insoluble oxalate, and thus prevents all further 
aCtion. In the important point of cheapness, nothing can 
be objected to in Mr. Nesbit’s process. 
Judging from our present knowledge the invention may 
be pronounced an easy, simple, and effectual means of 
overcoming a growing evil. 
