expansion and contraction of the metal as it warms 
and cools. 
| A slight inclination is necessary in laying them, 
about 1 inch in 12 feet, to take off the condensed wa- 
ter to the ends, where it is let out by the vents. 
We have three large Copper Valves, (a a a, Pl. 2.) 
one in the middle and one at each end of the great 
stove; they are for the purpose of letting out steam. 
These are fixed on the pipes, and are capable of fill- 
ing the house with vapour in an instant, thereby 
inereasing the heat, and produeing a fine dew 
all over the plants. A representation of one of these 
- is given (Plate, 2, fig. 2.) By turning over the ball 
the valve rises and opens the whole bore. of the pipe, 
as shown in the dotted line. 
Perhaps it may not be amiss to state some of Ee 
motives which induced us to adopt the above 
England «during the last twenty-five years, which ma 
without much impropriety be termed the period of 
the decline, if not the fall, of that interesting pursuit. 
“Several causes have contributed to bring hot-houses 
into neglect: of these, undoubtedly the pressure of 
propensities, vastly more expensive in their nature; 
and capable of affording far less real pleasure, have 
rapidly increased and are still in: 
The want of a place where some of hl fine pro- 
duetions of the Tropics may be seen unfolding their 
majestic forms, so different the unassisted 
growth of our island, has been one cause of the in- 
with which they have been treated. It is 
