water mains for
the towns of Coulommiers and Aix-en-Provence. The pipes were formed of
concrete in the trench itself. The mould into which the concrete was
stamped was sheet iron about two yards in length. The several pipes
were not specially joined to each other, the joints being set with
mortar. The concrete consisted of three parts of slow setting cement
and three parts of river sand, mixed with five parts of limestone
debris. The inner diameter of the pipes was nine inches; their
thickness, three inches. The average fall is given at one in five
hundred; the lowest speed of the current at one foot nine inches per
second. To facilitate the cleaning of the pipes, man-holes are
constructed every one hundred yards or so, the sides of which are also
made of concrete. The trenches are about five feet deep. The work was
done by four men, who laid down nearly two hundred feet of pipe in a
working day; the cost was about ninety-three cents per running yard.
It is claimed as an advantage for the new method that the pipes adhere
closely to the inequalities of the trench, and thus lie firmly on the
ground. When submitted to great pressure, however, they have not
proved effective, and the method, consequently, is only suitable for
pipes in which there is no pressure, or only a very trifling one.

* * * * *

THE SELLERS STANDARD SYSTEM OF SCREW THREADS, NUTS, AND BOLT HEADS.

_____________________________________________________
| |
| SCREW THREADS. |
|_____________________________________________________|
| | | | | |
| Diam. |Threads | Diameter | Area of | Width |
| of | per | at root of | Bolt at | of |
| Screw. | inch. | Thread. | root of | Flat. |
| | | | Thread. | |
|________|________|_________________|_________|_______|
| | | | | | |
| 1/4 | 20 | .185 | 13/64 | .026 | .0062 |
| 5/16 | 18 | .240 | 15/64 | .045 | .0074 |
| 3/8 | 16 | .294 | 19/64 | .067 | .0078 |
| 7/16 | 14 | .344 | 11/32 | .092 | .0089 |
| 1/2 | 13 | .400 | 13/32 | .125 | .0096 |
| 9/16 | 12 | .454 | 29/64 | .161 | .0104 |
| 5/8 | 11 | .507 | 33/64 | .2