TRANSACTIONS OF SECTION G. 603 
In any given set of experiments A will be the condensation corresponding to the 
heat loss per lin. foot when the flow is zero, and will decrease as the velocity increases 
until the frictional heat is equal to that lost through the walls when A will be zero. 
For velocities greater than this the steam initially dry will be superheated down the 
pipe and a modification of the above expression becomes necessary. 
] 
In the case of a covered pipe aa is always small, and can be neglected without 
serious error. 
A series of experiments have been carried out on a pipe } ins. internal diameter and 
75 feet long ; the pressure drop, the heat lost through the walls, the velocity of flow, 
etc., were measured. The velocities were varied from 30 to 200 feet per sec., and the 
initial pressures from 9 to 215-lbs. absolute. 
The results can be represented with considerable accuracy by 
py! — pal = 794 whs? 
for the particular steel tube used, the pressures being in lbs. per square inch, and w 
being the weight flow in lbs. per minute. 
The experimental work is still in progress, and the effect of diameter is being 
investigated. 
7. Bank Note Engraving. By A. KE. Bawrres, F.R.P.S. 
It is universally admitted that geometrical engraving is ideal for bank-note 
work, since its regularity increases the difficulty of counterfeiting, unless the 
forger has in his possession suitable machinery. 
The machinery in general use reached its present form nearly half a century 
ago, with the result that the forger has equipped himself as well as the bank- 
note engraver. 
Intaglio plate printing has defied accurate reproduction till the year 1912, 
when a process was exhibited at the Royal Photographic Society which renders 
this class of work the easiest of all kinds of printing to copy in facsimile. 
This process calls for neither skill on the part of the operator, nor costly nor 
elaborate appliances. 
Various systems of elaborate colour-ground have been tried upon bank-notes. 
Though these have in some cases successfully defied direct photographie repro- 
duction, they have all failed, either because the forger knows all about the 
engraving machinery, or because the nature of all such grounds producible by 
the machinery hitherto available has necessarily exposed them to reproduction by 
a process in which the repeated sections are photographed separately and a paste- 
up of the complete design produced from these components by photo-lithography. 
Figure studies, views, and other pictorial work possess no security, since their 
line structure is only obvious to an expert, and the forger can reproduce the tone 
values by ordinary photo-mechanical processes in common use. 
It is therefore essential that security printing must be geometrical in charac- 
ter; it must be free from the characteristic repetition of sections produced by 
the pentagraph and transfer engraving process; the character of the engraved 
work must be unmistakably and completely different to that in which time and 
text-books have made the forger himself expert. 
The new system of engraving, which has now been adopted by the Newfound- 
land Government, as well as some of the most prominent bankers for notes, and 
financiers for bonds, &c., is the only system that fulfils the above conditions. 
It also embodies numerous features of security which could not be incorporated 
in older methods of engraving, e.g. :— 
1. While ordinary engravers’ stock of sections is repeatedly used, sometimes 
upon photographically protected work, and at others for ornamental purposes, 
where the forger can easily photograph it, in the new system security and 
ornamental stock are kept apart. 
2. Bond coupons cannot be adequately protected through the limitations of 
existing machinery, while the new system specially lends itself to the engraving 
of these awkward little notes. 
