Atmospheric Moisture to Hot-houses. 287 



given as the day advances, the atmosphere assimilates itself in 

 some degree to that of a tropical day ; the dew point being 5" 

 or 6° below the temperature. At night the same dew recurs, 

 sprinkling is rendered unnecessary, and the fine rootlets, which 

 bristle into the atmosphere like the spines of a hedgehog, pre- 

 serve their extremities in full health and absorbing power. In- 

 deed the bulbs of my older stanhopeas are buried in their own 

 rootlets, like the birdsnest-looking masses of imported plants. 

 I believe it impossible to provide an atmosphere more congenial 

 to them. 



There is only one inconvenience which arises from any method 

 of moistening the atmosphere, and which of course increases in 

 proportion to the degree of moisture produced, viz. a drip from 

 the glass, which is often fatal to Orchidese, and injures the leaves 

 of all plants. At one time this caused me much annoyance. By 

 the following expedient I have rendered it a most valuable auxi- 

 liary, and should be much at a loss without it. The bars of my 

 lights being made as smooth as possible, I fix at intervals, say 

 from 15 in. to 18 in., all down them, small pieces of cobbler's 

 wax (putty would do as well, but is less easily removed), which 

 cause the drip to fall wherever I please ; and by thus subdividing 

 a bar into small spaces, no one drip is excessive. But this is not 

 all. Many of my plants are suspended on brass rods or chains, 

 fixed from rafter to rafter, under the lights : the dripping points 

 are arranged with reference to these, so that each plant receives 

 a small but constant supply of moisture, which is not allowed 

 to fall on the shoots themselves, but is generally received by a bit 

 of tile, or a little patch of sand. 



It remains that I should notice the defects of the cisterns ge- 

 nerally employed in hot-houses, especially those intended for 

 Orchidese. Many of my friends, to whom I have recommended 

 the use of large cisterns, have replied that such cisterns have been 

 repeatedly tried without any good effect ; and certainly I have 

 seen large and expensive cisterns in many hot-houses from which" 

 no benefit could possibly be derived ; they are generally con- 

 structed in the middle of the house in place of a pit, and are mostly 

 of stone or cement. Now, for a cistern to be of any use, it is 

 essential that the water should be at least 5° hotter than the mean 

 temperature of the house ; whereas the cisterns alluded to are 

 always from 5° to 1 0° lower than that mean. They are formed 

 of non-conducting materials, placed generally lower than the 

 flues or heating pipes, and from time to time filled up with cold 

 water, which warms very gradually; whereas, to answer any 

 purpose, the cistern should be formed of good conducting ma- 

 terials, and its bottom be placed higher than the flues or heating 

 pipes. Slate is the only material well adapted for such a purpose ; 

 a cistern built in cement, over flues or pipes, would be always 



u 4. 



