426 On the Construction of Kitchen 



the outside in every part except the bottom, which 

 should not be japanned. 



The reason why I have not made these tin tea- 

 kettles double is this : Tea-kettles are commonly used 

 merely for making water boil, which, with the kettles 

 here recommended, can be done in a very short time, 

 consequently much heat cannot possibly be lost during 

 that process in consequence of the top and sides of the 

 kettle being exposed naked to the cold air of the atmos- 

 phere. Were these utensils designed for keeping water 

 boiling-hot a great length of time, the case would be very 

 different ; and then it might be well worth while to make 

 them double, in order more effectually to confine the 

 heat in them. 



The saving of time in making them boil by making 

 them double would be very trifling indeed, for till the 

 water has become very hot there is but little loss of 

 heat through the sides and top of the kettle ; the com- 

 munication of heat being rapid in proportion as the 

 temperature of the hot body is high compared with 

 that of the colder body into which the heat passes. 



If a tea-kettle filled with water at the temperature of 

 the atmosphere at the time, on being put over a fire, be 

 brought to boil in 10 minutes, it will, during that time, 

 have lost only half as much heat as it will lose in the 

 next 10 minutes, if it be kept boiling-hot during that 

 time. 



All these kettles are of such forms as will render it 

 very easy to cover them, should it be thought advisable 

 to make them double ; and by covering them with plated 

 or gilt copper they may be made very elegant at a small 

 expense. 



