by the constantly varying strain of the bars.

Iron has been frequently and strongly recommended in the construction of
horticultural buildings. It has been used, with very satisfactory
results in England, and doubtless it may there be found to be the best
and most economical material for such purposes. It has been tried also
in this country, but the experiment has not resulted so favorably. The
main difficulty is that, in this climate, the expansion and contraction
of the iron rafters and bars are so great that the glass is continually
and badly breaking, and it is very difficult to keep the joints tight
enough to repel the rain and the cold air. There can be no doubt that in
this country, wood is a better material than iron for these purposes.

Thick and double thick glass has heretofore been used almost exclusively
for first class houses, but the high price of glass has of late,
compelled the use of a thinner article. It is generally believed that
thick glass will resist hail storms better than thin, but on this
question practical men differ in their opinions. It is contended, on the
other hand, that the elasticity of the thin panes resist a blow better
than the unyielding thick one, also that the latter is more likely to be
broken by the accumulation of water between the laps of the glass.

We have found that the 8 by 10 size of single thick French window glass,
second or third quality, is sufficiently good for Horticultural
buildings, and we do not use any other, unless especially called for by
the proprietor.

Glazing is often badly executed, half an inch lap, and sometimes more,
being often allowed to the glass, from the mistaken idea that rain, in a
driving storm, will find its way through. A lap of one-eighth of an inch
is amply sufficient in any case. The glass should be well "bedded" down
to the sash bar, in putty containing a portion of white lead, and well
secured with small iron nails or glaziers points. All putty should be
removed from the outside when the work is finished, and the sash bars
should then be painted with a heavy coat of thick paint which will close
up the joints and render them water tight.

Ample ventilation should be provided both at the top and bottom of
houses, so that large quantities of air may be supplied when necessary,
as in ripening the wood of vines in graperies, and in "hardening off"
plants in green houses before removal to the open air.

By reference to the numerous desig