THE 



586 



THI 



and its boiling point, 212°. Reaumur's 'plexicaule, a green - house evergreen 

 thermometer was that chiefly used in shrub ; increased by cuttings, and grow- 

 France before the Revolution, and is ^ ing best in loam and peat; the herba- 

 that now generally used in Spain, and j ceous kinds increase by division or 



seeds, and require a chalky soil. 



THESPESIA. Two species. Stove 

 evergreen trees. Half-ripe cuttings. 

 Sandy loam. 



THIBAUDIA. Four species. Stove 

 evergreen shrubs. Cuttings. Turfy loam, 

 peat, and sand. 



THINNING. The exhaustion conse- 



in some other Continental States. In 

 its scale, the freezing point is C ; and 

 the boiling point, 80°. Celsius or the 

 Centigrade thermometer, now used 

 throughout France, and in the northern 

 kingdoms of Europe, the freezing point 

 is 0° ; and the boiling point, 100°. 

 Hence, to reduce degrees of tempera- 

 ture of the Centigrade thermometer and ! quent upon the production of seed, is 

 of that of Reaumur to degrees of Fah- , a chief cause of the decay of plants. 



renheifs scale, and conversely: — 



This explains why fruit trees are weak- 



Rule 1. Multiply the Centigrade de- ened or rendered temporarily unpro- 

 grees by 9, and divide the product by ductive, and even killed, by being 

 5; or multiply the degrees of Reaumur allowed to ripen too large a crop of 

 by 9, and divide by 4 ; then add 32 to fruit, or to "overbear themselves," as 

 the quotient in either case, and the it is emphatically termed by the gar- 

 sum is the degrees of temperature ofjdener. 

 Fahrenheit's scale. The thinning of fruit is consequently 



Rule 2. From the number of degrees j one of the most important operations 

 on Fahrenheit's scale, subtract 32 ; ^ of the garden, though one of the least 

 multiply the remainder by 5, for Centi- : generally practised. On the weaker 

 grade degrees, or by 4 for those of branches of the nectarine and peach, 

 Reaumur's scale, and the product, in an average space of nine inches should 

 either case, being divided by 9, will be between each brace of fruit, and on 

 give the temperature required. | the most vigorous wood of the most 



To ascertain the internal temperature healthy trees, they should not be nearer 

 of a hot-house, the thermometer should than sis inches. This enforcement of 

 be fixed near its centre, against a pillar, the importance of thinning fruit, is not 

 and under a cupola, or little roof, shad- ; intended to be confined to the two 



ing it from the sun. 



trees specified ; it is equally important 



A self-registering thermometer should i to be attended to in all other fruit- 

 be in every house, for it shows the | bearers, but especially the vine, apri- 

 highest and lowest degrees of heat ■ cot, apple, and pear. It should be 

 which have occurred in the twenty- done with a bold fearless hand, and the 

 four hours; and, therefore, perfection of that which is allowed to 

 Fig. 166. serves as a check upon remain, will amply reward the grower 



in the harvest time for the apparent 

 sacrifice now made. But he will not 

 reap his reward only in this year, for 

 the trees, thus kept unweakened by 

 over production, will be able to ripen 

 their wood, and deposit that store of 

 inspissated sap in their vessels, so ab- 

 solutely necessary for their fruilfulness 

 a metal tube, perforated to next season. 



admittheheal, pointed so as The berries of the grape vine are best 

 to be easily thrust down and thinned from the branches with a sharp- 

 with a small door in the pointed pair of scissors, care being 

 side, for observing the de- taken to remove the smallest berries, 

 gree of temperature shown This increases the weight and excel- 

 lence of the bunches; for two berries 

 will always outweigh four grown on 

 the same branchlet of a bunch, be- 

 sides being far handsomer, and having 

 more juice, as compared with the skins. 

 The average weight of the bunches on 



serves as a check upon 

 those to whose care they 

 are entrusted. 



Bregazzi's bark-bed ther- 

 mometer is an excellent in- 

 strument for ascertaining 

 the bottom heat of hot- 

 beds, bark-pits, &c. It is 

 a thermometer inclosed in 



^ by the scale. Fig. 166 



THERMO PS IS. Three species. 

 Hardy or half-hardy herbaceous peren- 

 nials. Seeds. Light rich soil. 



THESIUM. Six species. Hardy 

 herbaceous perennials, except T. am- 



