CHAPTER 8.

Registering Operations

65. One great advantage which we may derive from machinery is
from the check which it affords against the inattention, the
idleness, or the dishonesty of human agents. Few occupations are
more wearisome than counting a series of repetitions of the same
fact; the number of paces we walk affords a tolerably good
measure of distance passed over, but the value of this is much
enhanced by possessing an instrument, the pedometer, which will
count for us the number of steps we have made. A piece of
mechanism of this kind is sometimes applied to count the number
of turns made by the wheel of a carriage, and thus to indicate
the distance travelled: an instrument, similar in its object,
but differing in its construction, has been used for counting the
number of strokes made by a steam-engine, and the number of coins
struck in a press. One of the simplest instruments for counting
any series of operations, was contrived by Mr Donkin.(1*)

66. Another instrument for registering is used in some
establishments for calendering and embossing. Many hundred
thousand yards of calicoes and stuffs undergo these operations
weekly; and as the price paid for the process is small, the value
of the time spent in measuring them would bear a considerable
proportion to the profit. A machine has, therefore, been
contrived for measuring and registering the length of the goods
as they pass rapidly through the hands of the operator, by which
all chance of erroneous counting is avoided.

67. Perhaps the most useful contrivance of this kind, is one
for ascertaining the vigilance of a watchman. It is a piece of
mechanism connected with a clock placed in an apartment to which
the watchman has not access; but he is ordered to pull a string
situated in a certain part of his round once in every hour. The
instrument, aptly called a tell-tale, informs the owner whether
the man has missed any, and what hours during the night.

68. It is often of great importance, both for regulations of
excise as well as for the interest of the proprietor, to know the
quantity of spirits or of other liquors which have been drawn off
by those persons who are allowed to have access to the vessels
during the absence of the inspectors or principals. This may be
accomplished by a peculiar kind of stop-cock--which will, at
each opening, discharge only a certain measure of fluid the
number of times the cock has been turned being registered by a
counting apparatus accessible only to the master.

69. The time and labour consumed in gauging the contents of
casks partly filled, has led to an improvement which, by the
simplest means, obviates a considerable inconvenience, and
enables any person to read off, on a scale, the number of gallons
contained in any vessel, as readily as he does the degree of heat
indicated by his thermometer. A small stop-cock connects the
bottom of the cask with a glass tube of narrow bore fixed to a
scale on the side of the cask, and rising a little above its top.
The plug of the cock may be turned into three positions: in the
first, it cuts off all communication with the cask: in the
second, it opens a communication between the cask and the glass
tube: and, in the third. It cuts off the connection between the
cask and the tube, and opens a communication between the tube and
any vessel held beneath the cock to receive its contents. The
scale of the tube is graduated by pouring into the cask
successive quantities of water, while the communication between
the cask and the tube is open. Lines are then drawn on the scale
opposite the places in the tube to which the water rises at each
addition, and the scale being thus formed by actual
measurement,(2*) the contents of each cask are known by
inspection, and the tedious process of gauging is altogether
dispensed with. Other advantages accrue from this simple
contrivance, in the great economy of time which it introduces in
making mixtures of different spirits, in taking stock, and in
receiving spirit from the distiller.

70. The gas-meter, by which the quantity of gas used by each
consumer is ascertained, is another instrument of this kind. They
are of various forms, but all of them intended to register the
number of cubic feet of gas which has been delivered. It is very
desirable that these meters should be obtainable at a moderate
price, and that every consumer should employ them; because, by
making each purchaser pay only for what he consumes, and by
preventing that extravagant waste of gas which we frequently
observe, the manufacturer of gas will be enabled to make an equal
profit at a diminished price to the consumer.

71. The sale of water by the different companies in London,
might also, with advantage, be regulated by a meter. If such a
system were adopted, much water which is now allowed to run to
waste would be saved, and an unjust inequality between the rates
charged on different houses by the same company be avoided.

72. Another most important object to which a meter might be
applied, would be to register the quantity of water passing into
the boilers of steam-engines. Without this, our knowledge of the
quantity evaporated by different boilers, and with fireplaces of
different constructions, as well as our estimation of the duty of
steam-engines, must evidently be imperfect.

73. Another purpose to which machinery for registering
operations is applied with much advantage is the determination of
the average effect of natural or artificial agents. The mean
height of the barometer, for example, is ascertained by noting
its height at a certain number of intervals during the
twenty-four hours. The more these intervals are contracted, the
more correctly will the mean be ascertained; but the true mean
ought to be influenced by each momentary change which has
occurred. Clocks have been proposed and made with this object, by
which a sheet of paper is moved, slowly and uniformly, before a
pencil fixed to a float upon the surface of the mercury in the
cup of the barometer. Sir David Brewster proposed, several years
ago to suspend a barometer, and swing it as a pendulum. The
variations in the atmosphere would thus alter the centre of
oscillation, and the comparison of such an instrument with a good
clock, would enable us to ascertain the mean altitude of the
barometer during any interval of the observer's absence.(3*)

An instrument for measuring and registering the quantity of
rain, was invented by Mr John Taylor, and described by him in the
Philosophical Magazine. It consists of an apparatus in which a
vessel that receives the rain falling into the reservoir tilts
over as soon as it is full, and then presents another similar
vessel to be filled, which in like manner, when full, tilts the
former one back again. The number of times these vessels are
emptied is registered by a train of wheels; and thus, without the
presence of the observer, the quantity of rain falling during a
whole year may be measured and recorded.

Instruments might also be contrived to determine the average
force of traction of horses--of the wind--of a stream or of any
irregular and fluctuating effort of animal or other natural
force.

74. Clocks and watches may be considered as instruments for
registering the number of vibrations performed by a pendulum or a
balance. The mechanism by which these numbers are counted is
technically called a scapement. It is not easy to describe: but
the various contrivances which have been adopted for this
purpose, are amongst the most interesting and most ingenious to
which mechanical science has given birth. Working models, on an
enlarged scale, are almost necessary to make their action
understood by the unlearned reader; and, unfortunately, these are
not often to be met with. A very fine collection of such models
exists amongst the collection of instruments at the University of
Prague.

Instruments of this kind have been made to extend their
action over considerable periods of time, and to register not
merely the hour of the day, but the days of the week, of the
month, of the year, and also to indicate the occurrence of
several astronomical phenomena.

Repeating clocks and watches may be considered as instruments
for registering time, which communicate their information only
when the owner requires it, by pulling a string, or by some
similar application.

An apparatus has recently been applied to watches, by which
the hand which indicates seconds leaves a small dot of ink on the
dial-plate whenever a certain stop or detent is pushed in. Thus,
whilst the eye is attentively fixed on the phenomenon to be
observed, the finger registers on the face of the watch-dial the
commencement and the end of its appearance.

75. Several instruments have been contrived for awakening the
attention of the observer at times previously fixed upon. The
various kinds of alarums connected with clocks and watches are of
this kind. In some instances it is desirable to be able to set
them so as to give notice at many successive and distant points
of time, such as those of the arrival of given stars on the
meridian. A clock of this kind is used at the Royal Observatory
at Greenwich.

76. An earthquake is a phenomenon of such frequent occurrence,
and so interesting, both from its fearful devastations as well as
from its connection with geological theories, that it becomes
important to possess an instrument which shall, if possible,
indicate the direction of the shock, as well as its intensity.
An observation made a few years since at Odessa, after an
earthquake which happened during the night, suggests a simple
instrument by which the direction of the shock may be determined.

A glass vase, partly filled with water, stood on the table of
a room in a house at Odessa; and, from the coldness of the glass,
the inner part of the vessel above the water was coated with dew.
Several very perceptible shocks of an earthquake happened between
three and four o'clock in the morning; and when the observer got
up, he remarked that the dew was brushed off at two opposite
sides of the glass by a wave which the earthquake had caused in
the water. The line joining the two highest points of this wave
was, of course, that in which the shock travelled. This
circumstance, which was accidentally noticed by an engineer at
Odessa,(4*) suggests the plan of keeping, in countries subject to
earthquakes, glass vessels partly filled with treacle, or some
unctuous fluid, so that when any lateral motion is communicated
to them from the earth, the adhesion of the liquid to the glass
shall enable the observer, after some interval of time, to
determine the direction of the shock.

In order to obtain some measure of the vertical oscillation
of the earth, a weight might be attached to a spiral spring, or a
pendulum might be sustained in a horizontal position, and a
sliding index be moved by either of them, so that the extreme
deviations should be indicated by it. This, however, would not
give even the comparative measure accurately, because a
difference in the velocity of the rising or falling of the
earth's surface would affect the instrument.

NOTES:

1. Transactions of the Society of Arts, 1819, p. 116.

2. The contrivance is due to Mr Hencky, of High Holborn, in whose
establishment it is in constant use.

3. About seven or eight years since, without being aware of Sir
David Brewster's proposal. I adapted a barometer, as a pendulum,
to the works of a common eight day clock: it remained in my
library for several months, but I have mislaid the observations
which were made.

4. Memoires de l'Academie des Sciences de Petersburgh, 6e serie,
tom. i. p. 4.