82 MASSACHUSETTS HORTICULTURAL SOCIETY. 



between them, presents many advantages for a considerable range 

 of glass. It is compact in the space required, and costs less for 

 construction and heating. 



The floor line of a greenhouse should usually be a few inches 

 above the outside grade. Storage pits are an exception, and are 

 generally arranged by covering an excavation with glass. As the 

 object is simply to keep the plants from freezing, a low tempera- 

 ture is all that is required. This can be obtained from the natural 

 heat radiated from the surfaces of the excavation, so that with a 

 proper covering for the glass no artificial heat is required. In 

 houses requiring a temperature of fifty degrees or more, such an 

 excavation under them increases the amount of fuel required to 

 maintain the temperature, as such surfaces, being below the tem- 

 perature of the house, absorb a portion of the artificial heat 

 supplied. 



Recently another form of house has been added to those already 

 so well known. It is a modification of the three-quarter-span 

 house, having the short slope of roof ou the southerly side. The 

 height of both sides is the same. The pitch of the northerly side is 

 from 22^° to 30°, and on the southerly side about 45°. The plant 

 tables are all on a level. It is claimed for this style of house that 

 in the dark winter months the sun's rays strike the glass at nearly 

 right angles, and that in consequence more of the rays enter the 

 house than through an ordinary pitch roof, and better results are 

 thereby obtained ; also that the low pitch ou the north side allows 

 the houses to be set up against each other in a manner similar to 

 the ridge and furrow system already described. The claim that a 

 greater number of effective rays of light enter the house where 

 they strike the glass at right angles, than would enter the house 

 through a longer plane of glass at a less pitch, is doubtful. A 

 long, flat glass roof on tlie north side, where the sun never shines, 

 to hold snow and ice until the warmth of the house melts it off, is 

 certainly a disadvantage which can readily be appreciated in this 

 latitude. Undoubtedly this style of roof admits a large amount 

 of light, but in this respect it has no advantage over a full span 

 roof running east and west. Architecturally it presents a very 

 awkward appearance. The level table plan keeps all the plants 

 except the front bench more or less in the shade of each other, 

 which is largely avoided in the arrangement of elevated tables 

 such as are usually adopted in regular three-quarter-span houses. 



