The Saint Paul globe. (St. Paul, Minn.) 1896-1905, 1897-04-19

In heavy ordnance not only is the.
weight computed without putting the
gun on the scales, but the center OF
gravity is determined within such D
hne point that when hung on it's trun-
mons the gun is SO nicely balanced
that it can be moved up and down
by the hand of one man. Swinging
bridges which move upon a pivot are
80 accurately balanced that hardly a
pound of difference exists between the
two Outstretched arms.
1t is necessary for an architect to
know the weight of his building long
before it is put up. The character of
his foundation depends upon it, Yet
the estimation Of this weight Is so
simple a matter that an under clerk
or an apprentice in an architects of
flee often gets the task Of calculating
1t. His grand total may reach, as in
the case Of the twenty -One-stOry Sure
ty building in this city, $4,000 tons, or
in the case of some big bridges like
the one at POughkeepsie, 1000 or 5000
tons. How is 1t done? In the first
place, the weight Of every piece of
material to become part of the struc-
ture is furnished by the manufacture
ers.
Whether it be Z-bar Orders or white
lead, it is all brought into the total
Even such an insignificant thing es a
difference in the quality and kind Of
paint used may make a ton difference
in the general weight Of the structure
Every rivet in the building is account
ed for, and if the ends are fused or
hammered down on the opposite side Of
a girder instead of being merely bolt
ed on the fact must be taken into ac-
count If the roof is covered with tin
the solder which holds the plates to-
gether is put down as weighing so
much per ingOt In laying the tin
a ~ oh
plate are Tapped over the adjoining
plates to the extent Of a quarter of an
inch on all sides. This quarter inch
of necessary lap adds a large number
of pounds to the general weight of the
reef So the process continues through
the whole building. The weights of
the clapboards, the plaster, the wall
paper, the window glass, the gas or
electric fixtures, the cOrnice ornaments
and Of the thousand and one materials
and appurtenanceS which go to make
up building are considered and ac-
counted for. In the aggregate these
weights, thousands of tons. constitute
merely the dead weight of the building
The live weight, such as the weight Of
the tenants. the furniture, and their
other belongings, must be added to the
total.
An office building with a capacity of
5000 persons would be about 165 tons
-
than in the daytime, when it is occu-
pied. In office buildings it is custom
airy to estimate about 100 pounds of
live weight to the square foot. In
residences about seventy pounds to the
square foot are calculated upon. In
manufacturing establishments it is
customary 10 allow for at least $50
pounds 20 the square foot The build
1ngs themselves press down upon the
earth at the various rates Of from
four tons to the square foot to twelve
or fourteen tons to the square foot
The tall st. Paul building is estimated
at the laSt-named figure. The Surety
building, mentioned above, is estimated
70 exert a pressure Of six tons to the
square foot.
The curious part of this business is
the testing of the ground on which tall
buildings are to stand. Nearly every
tester has his own method of ascer-
tanning earth resistance Some do it by
hydraulic pressure, some by pile driv-
ing. some by driving down into the
earth a worm which picks up dirt
and gravel and sand at various dis
t5nces and conveys them to the surface
70 be examined. The hydraulic method
is pursued by constructing q box of
casing, which is fastened tightly to the
ground. In it a plunger, operated by
Nster pressure, is made to press down
upon the earth. The force with which
4 presses on the ground is determined
~ its resistance to the inflow of the
water. which is ascertained beforehand.
IL driving piles these are forced down
simply until they viii so no further.
This is done at various points over the
ground on which the structure is to be
built. OF course, the depth of this point
OF greatest resistance can be marked
&C. 81 the beam of wood which has
gone down. The worm resembles a
carI,Screw If is hollow and as If twists
Its way down through the earth the
various strata OF the latter are forced
mp through the screw in the order in