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 |    .201 | .0113 |
|   3/4  | 10     |  .620 |    5/8  |    .301 | .0125 |
|   7/8  |  9     |  .731 |   47/64 |    .419 | .0138 |
|        |        |       |         |         |       |
| 1      |  8     |  .837 |   27/32 |    .550 | .0156 |
| 1-1/8  |  7     |  .940 |   15/16 |    .693 | .0178 |
| 1-1/4  |  7     | 1.065 | 1- 1/16 |    .890 | .0178 |
| 1-3/8  |  6     | 1.160 | 1- 5/32 |   1.056 | .0208 |
| 1-1/2  |  6     | 1.284 | 1- 9/32 |   1.294 | .0208 |
| 1-5/8  |  5-1/2 | 1.389 | 1-25/64 |   1.515 | .0227 |
| 1-3/4  |  5     | 1.491 | 1-31/64 |   1.746 | .0250 |
| 1-7/8  |  5     | 1.616 | 1-39/64 |   2.051 | .0250 |
|        |        |       |         |         |       |
| 2      |  4-1/2 | 1.742 | 1-23/32 |   2.301 | .0277 |
| 2-1/4  |  4-1/2 | 1.962 | 1-31/32 |   3.023 | .0277 |
| 2-1/2  |  4     | 2.176 | 2-11/64 |   3.718 | .0312 |
| 2-3/4  |  4     | 2.426 | 2-27/64 |   4.622 | .0312 |
|        |        |       |         |         |       |
| 3      |  3-1/2 | 2.629 | 2- 5/8  |   5.428 | .0357 |
| 3-1/4  |  3-1/2 | 2.879 | 2- 7/8  |   6.509 | .0357 |
| 3-1/2  |  3-1/4 | 3.100 | 3- 3/32 |   7.547 | .0384 |
| 3-3/4  |  3     | 3.317 | 3- 5/16 |   8.614 | .0413 |
|        |        |       |         |         |       |
| 4      |  3     | 3.567 | 3- 9/16 |   9.993 | .0413 |
| 4-1/4  |  2-7/8 | 3.798 | 3-51/64 |  11.329 | .0435 |