Hothouse roofing materials

2084. Arrangements for covering the roofs of hothouses by boards, canvas, or mats, to be lifted or rolled up or down, might be easily contrived, and advantageously used; but, except in pits and low hothouses, they are not thought worth attending to; it being considered better to gain the admittance of all the light possible, than to lose it for the sake of a little economy in fuel.