WASPS AND FLIES. 



556 



WATER. 



well-constructed boiler the water will lose 

 60 of heat hourly, and 200 cubic feet of 

 air are heated i per minute by every foot 

 of 4-inch pipe ; it is easy, by cubing the 

 contents of the building to be heated, and 

 dividing it by 200, to calculate the quan- 

 tity of pipe requisite to heat the building 

 to the required temperature. When the 

 temperature to be attained is 60, the 

 divisor should be 30 ; where it is to be 75 

 or 80, 20 will be nearer ; making allow- 

 ance always for loss by ventilation and the 

 radiating power of glass, which is about 

 one degree for every square foot and a 

 half, and bearing in mind also that where 

 smaller pipes are used the body of water is 

 smaller, and, consequently, the friction 

 greater ; for instance, in 2-inch pipes, the 

 difference of temperature between the flow 

 and return pipe will be four times greater 

 than in a 4-inch pipe. The above state- 

 ment must be regarded as approximate 

 rather than exact, and is given here more 

 to illustrate the theory of warming by hot 

 water than to lay down any precise rules 

 for heating any glasshouse by the circula- ' 

 tion of hot water. Nothing is better or 

 safer than this mode of warming, produced 

 by fire placed below a properly constructed 

 boiler. The heating power should be 

 without the greenhouse, whether it be pro- 

 duced by coal, gas, or oil. Many con- 

 trivances, more or less useful, have been 

 introduced for heating by hot water, pro- 

 duced by the agency of coal or gas, but 

 none are so useful and reliable as the 

 ordinary system of stove, boiler, and pipes, 

 in which the heating agency is fire 



Wasps and Flies. 



Winged insects of this description prove 

 highly destructive to fruit, especially wall 

 fruit, that is approaching maturity. Wasps 

 will eat away the pulp under the skin and 

 round the stone of plums, &c., until little 

 else but skin and stone is left. The best 



means of protection is the simple contri- 

 vance shown in Fig. I, which represents a 

 bottle containing some kind of syrup, or 

 sugar and beer mixed together, with a 

 piece of string round its neck, from which 

 issue other pieces, attached to hooks of 

 wire, by which the bottle can be suspended 

 to a branch of the tree on which the fruit 

 is ripening. The mouth of the bottle 

 should not be too wide, and it should 

 possess a good shoulder, against which 

 the insects will strike when attempting to 

 fly upwards before getting immersed in 

 the syrup below. As many of these traps 

 may be placed about a tree as may be 

 thought necessary. The same appliance 

 may be used within doors, but for placing 



FIG. I. HOTTLE TRAP 

 FOR WASPS AND FLIES. 



on the shelves of greenhouses a glass 

 vessel, shown in Fig. 2, standing on sup- 

 ports and open at the bottom, sold at prices 

 ranging from 6d. to is., will be found use- 

 ful. There is an interior rim rising from 

 the orifice underneath, which, with the 

 external portion of the contrivance, forms 

 a, circular trough, in which syrup can be 

 placed. The wasps and flies crawl under 

 the vessel and make their way inwards and 

 upwards, but none that enter ever make 

 their escape. This glass may be suspende^ 

 in any convenient situation by a piece of 

 string tied round the knot at the top. 



Water. 



A good deal of our success in growing 



