No. XXII.] APPENDIX. 311 



Tte time lias long sinoe passed away when scientific men would think 

 of attempting to devise an inimitable note. A note to be inimitable must 

 be made with a skiU superior to the power of imitation of all men. The 

 doctrine of inimitability should be buried with that of the phUosopher's 

 stone and the elixir of life ; nevertheless, cei-tain properties are demanded 

 by the mercantile community, whereby a man may readily determine a 

 good note. In this matter constancy of appearance is of paramount 

 importance, and in this particular the new surface note stands pre- 

 eminent. The vignette is printed in every impression line for line invari- 

 ably the same. The same expression of face is constantly maintained ; the 

 same number of lines in one impression is visible in the second, and, 

 however many thousands of notes may be issued, not the slightest possible 

 variation within certain limits can exist. Moreover, the note is printed 

 with a similar ink, and the same tone of colour preserved, that the public 

 laay be familiarised with a constant standard, and a uniform appearance 

 will be marked in their mind. 



Probably many of the members may recollect that the Society of Arts 

 many years ago very warmly entered into the question of inimitable notes, 

 and a very interesting little volume was issued by them on the subject. 

 Some of these proposals were remarkable from the intricacy of their 

 designs, but so far as the protection of the Bank is concerned no such 

 intricacy is required, as the Bank is never at a loss to detect a forged 

 impression, be it executed ever so skilfully, and the system ptirsued 

 by the Bank is so perfect that no forged note has ever escaped eventual 

 detection. 



The doctrine even of difi&cult imitation is one which must be studied 

 by physiological principles, and must be considered in reference to the 

 faculties of the eye and the properties of the mind. By actual measure- 

 ment I have ascertained that the eye can see perfectly over a range of 

 2° 18', which for twelve inches' distance would represent a space of half an 

 inch diameter. However, it has been ascertained by other philosophers 

 that an impression on the eye lasts for the one-tenth of a second, wherefore 

 it follows, to look over very carefully every part of a note, no less a time 

 than a third of a minute would be consumed, and probably in practice 

 three times as much would be required. As nearly 30,000 notes are daily 

 presented for examination, it follows that one gentleman must be employed 

 166 hours to inspect every single portion thoroughly. Practically, however, 

 the work is perfectly performed by nineteen inspectors, and therefore they 

 cannot enter into a minute and elaborate examination of every part of 

 every note, but only judge by the general appearance of aU manifestly 

 good notes : ajid a careful examination of any one where there may be 

 primd facie grounds for suspicion. 



From such causes it is found by long experience, that any ^tra- 

 ordinary complexity is not only useless, but delusive and dangerous, from 

 leading the mind into details which cannot be successfully appreciated. 

 The labour and exhaustion produced by minute inspection of any very 

 fine work for any length of time is shown by experience to be great, 

 and, though to the psychological surgeon it presents many features of 

 intense interest, yet the limits of this paper forbid me to enter into its 

 consideration. 



In speaking of identity, there is also another property of the eye to be 



