160 MISCELLANEOUS ARTICLES USED IN HORTICULTURE. 



immediately under it, or on the top rail of the uppermost sash 61' the roof. 

 This cord must be at least twice the length of the mat, in order that, when 

 the mat is drawn down and rolled up, the end of the cord may be within 

 reach of the operator on the ground at the front of the house. Another 

 ring ought to be fixed to the centre of the lower end of the mat, for the 

 purpose of fastening it to the front sill when it is drawn over the roof. When 

 the mats are removed from the roof, and rolled up during the day, the 

 cord is loosened from the ring, and lies on the roof, ready to be refastencd to 

 it, to draw the mats up the next evening. A second layer of mats might be 

 drawn up over the former, hi a direction across the sashes, so as to throw off 

 the rain in the manner of thatch, by attaching a cord to one corner of each 

 end of the mat, passing these cords over two pulleys, and laying on the mats 

 like tiles on a roof. Drawing up two mats, however, the one immediately 

 over the other, would be much less trouble, and would, excepting in the 

 cases of heavy rains or thawing snows, keep out the cold sufficiently well. 

 Where the roof is divided by wooden rafters, the mats should be exactly the 

 width of the sash, so as to fit in between them : but where it is not so divided, 

 the mats should overlap one another in the manner of slates that is, one 

 half the number of mats should first be drawn up, leaving half the width of 

 a mat between each, and afterwards the remaining half should be drawn up 

 so as to cover the intervening spaces, and overlap a foot over the mat at each 

 side. It is much to be regretted that mats of this kind are so little used in 

 England, especially in country places, where straw is abundant and cheap ; 

 for being made at a time when little other work can be done, and of a mate- 

 rial of very little value, and retaining heat much better than any other 

 covering, they would prove a great saving of fuel and of the labour of 

 attending on fires, as well as insure the safety of plants. Mr. Shennan, a 

 gardener of great experience, who used these mats extensively, observes, in 

 the Gardener's Magazine for 1827, that he considers the revival of the old 

 system of covering with straw or reeds, and the system of heating by water, 

 as the greatest improvements that have been introduced into the forcing 

 department in his time. 



446. Wooden fihutters form an excellent covering for the sashes of pits and 

 frames ; and though they are more expensive at first, yet from their great 

 durability when kept well painted, they are found by market-gardeners to 

 be the cheapest of all coverings in the end. Boards do not retain heat so 

 effectively as reeds or straw, but they exclude rain and wind better than 

 that material ; and by being kept an inch or two above the glass by the 

 cross-bars which bind the boards together, a space is left sufficient to check 

 radiation, and to prevent the escape of heat by conduction. If boarded shut- 

 ters could be kept about six inches from the glass, and air excluded from 

 entering at top and bottom and at the sides, radiation would be effectually 

 returned, and less risk of the escape of heat by conduction incurred than 

 when the boards touch the sash-bar ; but this would require great care in 

 excluding the air from the sides and ends. All the frames and pits in the 

 gardens at Syon are covered by boarded shutters, and all those in the exten- 

 sive forcing-ground of Mr. Wilmot of Isleworth. Narrow shutters of this 

 kind might be contrived for hothouse roofs, so as to produce a great saving 

 of heat. Canvas would, in many instances, repel wet and check radiation 

 as well as deal boards, and might be put on much quicker ; but the great 

 objection to it is its liability to be disturbed by high winds, unless, indeed, 



