THERMOMETER FOR HOTBEDS. 498 THORN AND CHIEF VARIETIES. 



heit's scale and at o in the Centigrade 

 scale, and consequently in the former, 

 boiling point is at 212. The comparative 

 graduation of the thermometer according 

 to the two scales named is shown in the 

 accompanying illustration, which does not 

 go up to the boiling point, but which 

 exhibits a range sufficient for all ordinary 

 purposes. Common thermometers, suffi- 

 ciently accurate for all practical purposes in 

 garden work, may be bought at is., 2s., 

 and 35. each, but self-registering thermo- 

 meters, which show the extreme points to 

 which the mercury has fallen by night or 

 risen by day, which are useful in hothouses, 

 cost far more. The price of these may be 

 ascertained from any makers of instruments 

 of this description, who should be told the 

 purpose for which it is required, and con- 

 sulted as to which it is best to purchase 

 for the object in view. 



Thermometer for Hotbeds. 



In ascertaining the temperature of hot- 

 beds, &c., it is as well to place the 

 thermometer in a metal case with one of 

 its sides made of glass, and to make an 

 excavation, in the bed, and lay the box 

 and the thermometer within it in the 

 excavation, when a few minutes will serve 

 to show the temperature of the bed. 

 This is a better plan than that of simply 

 laying the thermometer on the surface of 

 the bed or than plunging the instrument 

 itself into the bed. Instruments are 

 made for ascertaining the temperature of 

 the ground, which are called geo-thermo- 

 meten, or ground thermometers. Of these, 

 Begazzi's Bark Bed Thermometer is com- 

 monly used for determining the temperature 

 of hotbeds, vinery borders, &c. It consists 

 of a thermometer about 2 feet long, en- 

 closed in a copper tube, in the top of 

 which is placed a wooden cylinder on 

 which is marked the scale, and viewed 

 by a small door, to the inside of which 



another small thermometer is fixed, so 

 that the temperature of the air above the 

 bed may be shown at the same time. 

 Such an instrument, however, is by no 

 means absolutely necessary, as the tem- 

 perature can be determined as nearly as 

 possible, for practical purposes, by adopt- 

 ing and following the plan described 

 above. 



Thinning Out. 



A term applied to the act and work of 

 removing shoots and branches of fruit-trees 

 that are either unnecessary or in the way, 

 and which, if left, would, with those that 

 remain, be too numerous for the tree to 

 support, and at the same time yield fine 

 fruit. It is also applied to the removal of 

 seedling plants sown in rows or drills, or 

 even broadcast, as turnips frequently are, 

 the removal of intermediate plants, leaving 

 others at certain distances from each other, 

 giving room to those that remain to grow 

 to their proper size. 



Thorn and Chief Varieties. 



The genus Crat&gus, the thorn or ha\\ 

 thorn, is a large one, for which care and 

 cultivation have done much. Flowering 

 and fruit-bearing, various in colour and in 

 growth, the whole family is worthy of a 

 place wherever there is room for planting. 

 So hardy are they, that the most severe 

 frost will never injure them, and so easy 

 of culture, that they do not refuse to grow 

 in almost any soil, and under a smoky 

 atmosphere. Amongst the best and most 

 useful varieties may be named Cratcegus 

 apiifolia, the parsley-leaved thorn ; C. 

 Maroccana, or Maura, the Morocco thorn ; 

 C pendula^ the weeping hawthorn ; and 

 C. rubra, the red-fruited hawthorn. Of 

 the varieties of the common hawthorn, C. 

 oxycantha,) C. 0. punicea, a scar let -flowered 

 thorn, and C. o. plena and C. o. puniceo 

 flore-pleno* white and scarlet doybje- 



