VEGETABLES UNDER GLASS. 189 



fully made, and the " heat " is of uuiforin quality, they work very 

 well, aud in skillful hands produce excellent crops, especially in 

 the latter part of winter and in spring ; Ijut for all- winter work 

 the greenhouse is far preferable. 



As I said before, it is now about twenty-eight years since some 

 of the enterprising gardeners of Belmont and Newton began to 

 experiment in building greenhouses for growing lettuce. The first 

 houses were built of hotbed sashes, the experimenters having so 

 little confidence in the success of the plan that they were unwilling 

 to risk a permanent roof, which could not easily be pulled down 

 and used again for hotbeds. It was then the common belief that 

 lettuce must be grown within a few inches of the glass, aiid the 

 houses were built low, with just room enough above the beds to 

 work them, and with the roof almost as fiat as a hotbed. It was 

 soon found, however, that lettuce equally good grew at several 

 feet distant from the glass, and that it was better to give the roof 

 more pitch in order to shed snow and rain. The houses now built 

 for this purpose have a pitch of from twenty to twenty-five de- 

 grees, and some of them are four hundred feet long and fifty feet 

 wide, with a ridge twenty feet above the beds. It is found that 

 these houses are far better than hotbeds for winter growius; of 

 lettuce and cucumbers, and the increase of glass during the last 

 five years has been chiefly in the line of greenhouses, while not a 

 few additional houses have been covered with old hotbed sashes. 

 The permanent glass roof, however, is preferable unless it is 

 desired to remove the roof during spring or summer to work on 

 the beds, as is still practised by some gardeners. 



The amount of glass used for forcing vegetables, within ten 

 miles of Boston, is at present probably about fifteen acres, and of 

 this rather more than half is in greenhouses ; nearly four acres are 

 to be found on one farm, that of Mr. Warren W. Rawson of 

 Arlington. 



I have little to add to the excellent lecture you have recentl}^ 

 listened to from Mr. Burnham on the construction of greenhouses ; 

 the preference seems to be just now for glass about eighteen by 

 twenty-four inches and cypress lumber sash-bars, supported by 

 iron pipe for posts. In large establishments, steam has decided 

 advantages over hot water for heating. 



The large establishments keep a night fireman to tend the 

 boilers, burning bituminous coal, which not onh' is cheaper but 



