452

The total lift is thus 60 ft. 6 in. The canal is divided
into five levels, the length of which, respectively, is 20,},
75;, 21}, 3 and 2 miles.

The width of the canal at the top varies, of course, with
the slopes of the sides ; these are made ranging from I in
6 through rock to 2 to I in clay and soft material. Except

I when passing through rock, the slopes are pitched with

rough stone on a rubble backing to protect them from the
wash of passing vessels.

The total amount of excavations in the canal is about
47;} million cubic yards, one-sixth of which is in the rock.
The walling of the various locks contains about 7oo,ooo
cubic yards of concrete, exclusive of brickwork and mas-
onry ; the walls of the Manchester and Sallord Docks con-
tain about 6oo,Qoo cubic yards of concrete. The weight
of steel and ironwork in the fixed and swing bridges is
about 15,000 tons. J

The whole of the contract was let to the late Mr. T. A.
Walker, who died in November last, and the work is now
being carried on by his executors. The contract requires
it to be completed by December 31, 189i.

The work is divided into nine sections, each under
charge of a separate staff. A railroad and a telephone
line have been built the whole distance from Eastham to
Manchester. ‘

A
T

CONTRIBUTIONS TO PRACTICAL RAILROAD
INFORMATION.‘*

CHEMISTRY APPLIED TO RAILROADS.
XII.-—TI-IE WORKING QUALITIES OF PAINT.

Bv C. B. DUDLEY, CHEMIST, AND F. N. PEASE, Assisr-‘

ANT CHEMIST, OF THE PENNSYLVANIA RAILROAD.
(Copyright, 1889, by C. B. Dudley and F. N. Pease.)
(Contzbmezi from page 417.)

IN our analyses of the requisites of a good paint in the
last article, one point which has usually been regarded as
of very great importance in ‘paints, was overlooked, or at
least not mentioned, and this is what is technically known
as “ covering power.” This was not wholly unintention-
al. as we have always been somewhat skeptical of the com-
mon explanation of what is known as “ covering power.”
There is unquestionably a difference in different pigments,
as we ordinarily use them, in their ability ‘to hide a sur-
face, but we are not yet fully satisfied as to whether this
is an inherent difference in pigments, or is a difference of
physical condition. It may possibly be both, but we will
treat this subject more at length later.

Meanwhile, for the sake of having the subject clearly
before us, we will say that the requisites of a good paint
are, first, durability, which has already been discussed ;
second, that it shall work properly during its application ;
third, that it shall dry with sufficient rapidity, and fourth,
that it shall have the proper covering power. This article
will be more especially devoted to working qualities of
paint. -

Before beginning the discussion of the working qualities
of a paint. however, perhaps a little further analysis is
necessary. Painting may be divided, according to the use

* The above is one of a series of articles by Dr. C. 13. Dudley, Chemist,
and F. N. Pease, Assistant Chemist, of the Pennsylvania Railroad, who are in
charge of the testing laboratory at Altoona. They will give summaries of
original researches and of work done in testin materials in the laboratory
referred to, and very complete specifications of t e different kinds of material
which are used on the road and which must be bought b the Company.
These specifications have been prepared as the result of care til investigations,
and will be given in full, with the reasons which have led to their adoption.

The_articIes will contain information which cannot be found elsewhere.
No. I, in the JOURNAL for December, is on the Work of the Chemist on aRai1-
road _; No. II, in the anuary number, is on Tallow, describing its impurities
and adulterations, an their injurious effects on the machinery to which it is
applied ; No. III, in the February number, and No. IV, in the March num-
ber, are on Lard Oil; No. V, in the April number, and No. VI, in the May
number, on Petroleum Products; No. VII, in the June number, on Lubri-
cants 8n_d Burning Oils; N0. VIII, in the July number, on the Method of
Purchasing Oils; No. IX, also in the July number, on Hot Box and Lubricat-
ing Creases; No. X, in the August number, on Battery Materials; No.
XI, in the September number, on Paints. These chapters will be followed
by others on different kinds of railroad supplies. Managers, superintendents,
purchasing agents and others will find these CONTRIBUTIONS T0 PRACTICAL
RAILROAD INFORMATION of special value in indicating the true character of
the materials they must use and buy. — -

THE RAILROAD AND

[October, 1890,

to which the paint is put, and especially according to
whether it is expected to protect a surface or not, into two
classes. The first of these classes is generally known
under the head of “ house painting,” and covers the paint-
ing of all surfaces, where the paint itself is not only expect-
ed to give the appropriate color that is desired, but also to
protect the surface against the weather. The other kind
of painting is known as “coach painting,” in which the
color is the thing sought for, the protection of the surface,
and also of the coloring material of the paint being secured
principally by the varnish. These two kinds of painting
are characteristic and distinctive, and both require differ-
ent qualities in the material to be used. In our last article
only house painting was considered, although much that
was said in regard to durability in that article, will apply
equally well to varnish This is especially true of me-
chanical injury, the action of deleterious gases, the de-
struction during cleaning, and the action’ of water, which,
as will be remembered, were cited among others as causes
for the deterioration of paint. Indeed, we really do not
know of any additional cause, beyond the seven mentioned
in the last article, which interferes with the life and dura-
bility of varnish, except, perhaps, its cracking, and upon
this point we are hardly yet prepared to express any posi-
tive opinions. In what follows we will endeavor to recog-
nize the two kinds of painting.

In order that paint, to be used for house painting and
analogous purposes, should work well, two or three points
seem to be essential. First, it must not run off the work ;
second, the brush marks made during application must
disappear later ; and third, the work must not appear spot-
ted or streaked. In general these qualities are obtained
by what is commonly known as proper mixing, although
the grinding, the purity of the oil, and the kind of dryer used
all have influences.

The running of paint may be due to two or three causes.
The paint may be applied too thickly for the kind of paint
used ; for example, to put on as thick a coat of very thin
paint as paint containing a larger percentage of pigment,
would inevitably result in the paint running. Of course
linseed oil alone can be applied to a surface with a brush
without running, provided too much is not put on, and the
greater the percentage of liquid in a paint, the thinner the
coat must necessarily be. This application of thin coats
is a very common fault, especially in contract painting.
Where the pigment is strong in coloring and covering
power, the temptation is to put on very thin coats, which
temptation is increased by the fact that thin coats dry
quicker than thick ones. Of course with proper care in
using a very thin paint, there need be no difficulty from
running. Another éause which may lead to running is
want of proper grinding. The finer and better mixed the
pigment and liquid are, the less the tendency to run._ A
paint mixed up by simply stirring the dry pigment into the
liquid, is more apt to runthan one which has been ground.
The oil leaves the coarser portions of the pigment, and
carries off the finer portions with it, resulting in streaks
down the work. With proper proportions between the
liquid and pigment, this difficulty can be obviated,
but some pigments, as is well known, cannot be
ground, and are therefore always used by simply mixing
with the liquid, but a paint otherwise good and properly
proportioned may give difficulty from running, it it was
not finely enough ground. Still another cause of running
is too long a time after the paint is put on before it sets.
We have mixed up two paints, one of which would take a
set, although not dry, in from six to eight hours, and an-
other which would not take a set in twice that time, the
amount of pigment and liquid and the grinding being ex-
actly the same, and the second would run, while the first
would not. It is very easy to see why this should be so.
A thin layer composed of liquid and pigment, maintaining
its limpidity, and being in a vertical position for a long
time, will'run off from the surface more readily than one
which does not maintain its limpidity, although other things
are the same. The paint which takes a set, thereby loos-
ing its limpidity, resists the strain which produces the
flowing or running in the other paint. Adulterated oil,
especially linseed oil, containing petroleum product, is
liable to this same difliculty, and for the same reason,