MISCELLANEOUS ARTICLES USED IN HORTICULTURE. 129 



By the numbers in this table the temperature of the dew-point in 

 the general tables has been calculated, and these have been constantly 

 checked by direct comparison with Daniell s hygrometer at the Royal 

 Observatory, Greenwich, up to the year 1868, and found correct. 



Other most useful tables follow of the expansion of air by heat 

 the elastic force of aqueous vapour the weight and enlargement of 

 a cubic foot of air and vapour, at different temperatures and different 

 degrees of humidity, and a series of readings of the dry and wet bulb 

 thermometers in relation to these and other points from 10 to 100, 

 and these tables are indispensable to all who would thoroughly master 

 the subject. But it may be stated in general terms here that the 

 nearer the reading of the wet and dry bulb thermometer approximate 

 to each other, the more moist the air is, and the greater the disparity 

 the drier the air. For instance, in a plant stove at a temperature of 

 70, a genial atmosphere for the growth of plants would be secured 

 by the wet bulb thermometer reading 62 or 64. See ' Glaisher's 

 Tables.' 



Other articles of various kinds are required in gardens, of which it 

 will be sufficient to enumerate those which are most important. A 

 grindstone is essential in every garden ; because, unless tools and 

 instruments are kept at all times sharp, it is impossible that operations 



Fig. 101. can either be P r P erl 7 P er - Pi - 102 



formed, or a sufficiency of 



work done. Whetstones are 

 also necessary for scythes 

 and knives. Portable shoe- 



Zridge-plank Jor wheeling scrapers of cast-iron, for 

 across boa: or other edgings. u ^ g when coming off dug 



ground in wet weather on the gravel walks. One or 

 more bridge-planks, fig. 101, for wheeling across box- 

 edgings. Common planks for wheeling on when the 

 soil is soft, or when injury would be done by the 

 sinking of the wheels; and trestles for raising them as 

 scaffolding. Some hundreds of bricks and flat tiles for 

 forming traps for birds or mice, and for a variety of 

 purposes. A pair of leather bearing-straps for re- 

 lieving the arms in wheeling or in carrying hand- 

 barrows, fig. 102. Old fishermen's-netting, for pro- 

 tecting rising seeds from birds, and for covering 

 currant or cherry-trees for the same purpose, or for 

 protecting wall-trees, or for shelter. Finely-meshed 

 wire frames are likewise much used for protecting pur- 

 poses against birds, mice, &c. Live moss (commonly Leather bearing 

 sphagnum) for packing plants and for other purposes. f**op. 



Lime unburned, but broken into small pieces, in order to be burnt in 

 the hothouse fires, to supply quicklime as wanted for making lime- 

 water : quicklime will answer, if kept compressed in a cask or box, so 

 as to exclude the air. Potash, for using as a substitute for quicklime, 

 in preparing a caustic fluid for destroying worms, snails, &c. Refuse 



K 



