232 BEPORT— 1889. 



by the hydrostatic method of weighing in air and water, and it is not 

 difficult to lead children to understand this latter method after they have 

 determined the heights of balancing columns of liquids such as turpentine, 

 water and saturated brine, of which they have previously ascertained the 

 relative density. These hydrostatic experiments are of value at a later 

 stage in considering the effects of atmospheric pressure. 



By determining the dimensions of a cube and the weight of the water 

 which it will displace, an opportunity is afforded to point out that if the 

 results are expressed in cubic centimetres and grams respectively, there is 

 a practical agreement between the numbers, and hence, to explain the 

 origin of the metric system of weights and the relationship between its 

 measures and weights ; the irrationality of the English system may then 

 be explained. 



The relative densities of a large number of common substances having 

 been ascertained, the results may be tabulated and then the value of the 

 data as criteria may be insisted on ; as an illustration of their value, 

 quartz, flint, sand and gravel pebbles may be selected. The children 

 liaving determined their relative densities, the agreement between the 

 results ruay be pointed out and the identity of the material explained. 

 By drawing perpendiculars corresponding in height to the densities of 

 various substances, a graphic representation is obtained which serves to 

 bring out the value of the graphic method of representation. 



A very valuable exercise to introduce at this stage is based on the 

 well-known fact that in certain conditions of the atmosphere things 

 appear moist : a muslin bag full of seaweed may be hung up under cover 

 but freely exposed, and may then be weighed daily at a given time ; 

 simultaneously the state of the weather, direction of the wind, the height 

 of the barometer, and the state of the wet and dry bulb thermometer may 

 be noted; on tabulating the results, and especially if the graphic method 

 be employed, the variations and their relationship will be noticeable. 



The thermometer, having thus become a familiar instrument, may be 

 used to examine melting ice and boiling water ; the construction of both 

 the Centigrade and Fahrenheit thermometers may then be explained, and 

 the effect of heat on bodies made clear. The density of ice and of water 

 at various temperatures may then be determined, a Sprengel tube — which 

 is easily made — being used for warm water ; the bursting of pipes in 

 winter, the formation of ice on the surface of water, &c., may then be 

 explained. Afterwards simple determinations of the heat capacity of a 

 few metals, &c., and of the latent heat of water and steam, may be made 

 in accordance with the directions given in a book such as Worthington's 

 'Practical Physics.' 



Stage III. — Studies of the effect of heat on things in general; 

 of their behaviour xohen burnt. 



As it is a matter of common observation that heat alters most things, 

 the effects of heat on things in general should be studied ; in the first in- 

 stance qualitatively, but subsequently, and as early as possible, quantita- 

 tively. Bits of the common metals may be heated in the bowl of an 

 ordinary clay pipe plunged into a clear place in any ordinary fire, or in 

 such a pipe or a small iron spoon over a gas flame. The difference in 

 fusibility is at once apparent, and in the case of metals like iron and 

 copper it is noticeable that although fusion does not take place, a super- 



