pes, upon which they are commonly used abroad, when used on any, not
being yet much in use here.

In the estimates of Mr. Denton, in his tables, collars are set down at
about half the cost of the mixed tiles. The bore of them being large
enough to receive the end of the tile, increases the price in proportion
to the increase in size. It is believed, however, that a smaller size of
tiles may prudently be used with collars than without, because the
collars keep the tiles perfectly in line, and freely admit water, while
they exclude roots, sand, and other obstructions. A drain laid with one
and a half inch tiles with collars is, no doubt, better in any soil than
two-inch tiles without collars. Some compensation for the cost of
collars may thus be found in the less price of the smaller tiles.

6. _Laying._ The cost of laying tiles is so trifling as hardly to be
worth estimating, except to show its insignificance. The estimate, by
English engineers, is two cents per rod for "pipe laying and finishing."
What is included in "finishing," does not appear. From the personal
observations of the writer, it is believed that an active man may lay
from 60 to 100 rods of tiles per day, in ditches well prepared. Indeed,
we have seen our man James, lay twelve rods of two-inch tiles, in a
four-foot ditch, in forty-five minutes, when he was not aware that he
was working against time. This is at the rate of sixteen rods an hour,
which would give just 160 rods, or a half-mile, in a day of ten hours.

7. _Number of Tiles to the Acre._ The number of tiles used depends, of
course, upon the distances apart of the drains, and upon the length of
the tiles used.

The following table gives the number of tiles of various length, per
acre, required at different intervals:

========================================================================
Intervals between |Twelve inch|Thirteen inch|Fourteen inch|Fifteen inch
the Drains, | Pipe. | Pipe. | Pipe. | Pipe.
in feet. | | | |
------------------+-----------+-------------+-------------+-------------
15 | 2904 | 2680 | 2489 | 2323
18 | 2420 | 2234 | 2074 | 1936
21 | 2074 | 1915 | 1778 | 1659
24 | 1815 | 1676 | 1555 | 1452
27 | 1613 | 1489 |