It is well known that ordinary writing is easily removed when it is acted upon by bleaching agents. Advantage is taken of this fact by unscrupulous persons desirous of altering documents, cheques, and banknotes for improper purposes. Hence the number of fugitive inks and supposed untam-perable papers in use to meet this difficulty.

A curious and interesting case of supposed fraud came under my notice in the form of a document which was written upon the flyleaf or second page of a sheet of legal paper, the margin of the first page containing the stamp, date, and watermark of a will purporting to have been written about 20 years ago. The document or will was thus written upon paper bearing both on stamp and in watermark a date which gave it the semblance of age. The appearance of the document gave rise to suspicion, and I was asked if it was possible to tell the age of the writing, and if the writing had been executed at one and the same time, and if so at whit time.:

This was of course, impossible, as I was not allowed to treat the document itself. I had, therefore, to make experiments upon writings the dates of which I knew.

I selected writing 1 day, 6 months, 12 months, 2 years, 6 years, 14 years, and 22 years old, and exposed these writings to the action of a very dilute solution of ordinary bleaching powder in water. The specific gravity was about 1.001. In 6 minutes the newly written matter had disappeared; in 9-12 minutes the writing of 6 months ago had disappeared; in 20 minutes the writing of 2 years had partly disappeared; in a like time the writing of 6 years ago was not greatly affected; 14 years ago very slightly; and 22 years hardly affected at all (indeed, old writing seems hardly affected by such a weak solution, even after hours' exposure).

Peroxide of hydrogen acts more slowly, but gives more definite results. Other reagents give effects which help (although sometimes in a contrary manner to that I have indicated) to establish the fact that ordinary writing ink, which is a compound of gallic and tannic acids with proto-salts of iron, becomes more stable (presumably by oxidation), and consequently is less or more affected by chemicals which act upon the organic coloring matter of the ink. There are great varieties of writing inks, chromium and vanadium salts being .sometimes substituted for the iron salts. There are also black and colored inks prepared from coal tar dyes; but thinking it highly improbable that any documents intended for preservation would be executed in such evanescent inks, I did not investigate their behaviour under such treatment. When ink is thus bleached or apparently removed, most of the iron contained in , the compound remains mordanted with the fibres of the paper; consequently, writing so tampered with or dealt with can be restored by the application of gallic or tannic acid. The writing is thus reproduced almost in its original depth of color.

It is delicate work (especially in the civil legal aspect of the case to which I have referred) to determine in a reliable manner the age of any particular writing, and it is necessary that the following precautions be carefully observed:

1. The inks must be those known as ordinary writing inks, prepared from iron and chromium salts and galls.

2. Writing dried by means of blotting paper is naturally more easily removed than writing which is allowed to dry on the surface of the paper; and light writing is somewhat more easily removed than coarse and heavy writing.

3. The bleaching solution must be exceedingly dilute, otherwise the action is so rapid and powerful that both old and new writings are removed almost simultaneously.

4. The action must be carefully watched, so as not to be too long continued. Lastly, very old writing which has become brown by age, although it resists the action of weak solutions of bleaching powder and peroxide of hydrogen, will show signs of giving way almost instantly when acted upon by dilute nitric, hydrochloric, and oxalic acids.

Although I have only made use of a well-known process and materials to obtain the results I have indicated, still I think such a simple means of detection may act as a check to frauds which are becoming only too common. There was a most interesting paper read before the Literary and Philosophical Society of Manchester, in the session of 1879 and 1880, by Mr. W. Thomson, F.R.S.E., which I commend to the study of any one wishful to carry this investigation further than I have been able to do. In it the author gives many curious and interesting facts in connection with the behaviour of writing inks under the influences of various chemical compounds. (R. Irvine.)