ON STUDIES MOST SUITABLE FOR ELEMENTARY SCHOOLS. 511 



Heavy and light materials ; to compare heaviness of materials we must find 

 the weight of equal volumes of each. By finding the weight of one cubic centi- 

 metre of each substance, we can find their relative weight. Necessity for com- 

 paring all materials with one standard substance. The reason for telecting water 

 as this standard. The simplicity in the metric system of the connection between 

 weight and volume of water. 



Tabulation of results of weight of 1 c.c. of all materials previously measured. 

 Weight of unit volume of a substance a very general method of determinino- its 

 quality or the amount of adulteration. 



' Water finds its own level '; experiments to explain this statement. Columns 

 of liquid balanced in U-tube ; equality of level in tubes of equal and unequal bore. 

 The tiow of water in pipes of a town supply. 



Revision of the relative weights of 1 c.c. of water and of mercury, showino- 

 that mercury is about 13^ times as heavy as water. Columns of wafer balanced 

 against columns of mercury in (j-tube, showing that the water column is always 

 about 13^ times the length of mercury column; deduce the law of the u-tube, 

 and by it confirm the results previously obtained for weight of 1 c.c. of brine 

 and spirit. 



Simple experiments and illustrations to show the reality of air; water does 

 not fill a tumbler of air inverted iu a vessel of water ; air necessary to burning of 

 a fire and for breathing ; the blacksmith's bellows and the bicycle pump. Solids, 

 liquids, and gases. Air, an invisible gas like coal-gas, but having no smell, not so 

 easily recognised. Steam also an invisible gas. Inflate au indiarubber balloon ; 

 pump up a bicycle tyre ; pass air through water, and collect it by displacing water 

 from ajar inverted in water. Fill ajar inverted in water by sucking the air out 

 by means of a tube. 



In order to weigh air we must be able to expel it from a vessel. Show that it 

 may be expelled {a) by an exhaust pump, (b) by boiling water in the flask, (e) by 

 expansion by heat. Collect the air driven out of a flask by boiling water in the 

 flask, and thus show that all the air is expelled. Open a partially exhausted flask 

 under water. 



Weigh a flask first full of hot air, and then full of cold air; explain why hot 

 air rises, and its application to natural ventilation. Simple experiments to show 

 that ail' exerts a pressure on bodies; experiments with tubes of water and mercury 

 to show that there is a limit to the pressure of the atmosphere. 



The u-tube or siphon barometer ; the straight tube barometer. Changes in 

 height of mercury in barometer compared with changes in the weather. Daily 

 observations of barometer, kind of day, winds, direction, and strength ; height of 

 sun at midday. 



Note. — It is not desirable that tlie term ' density ' should be used in the first year's work ; 

 all results should be recorded as the weight of 1 cubic centimetre in grams. 



Second Year (about 12 to 13 i/ears of a(/e). 



Simple experiments with a lever having its fixed point (fulcrum) at one end to 

 show connection between the force (power) and the load it can rai^e. A. small 

 force can raise a heavy load, but the small force works through a greater distance 

 than the load is raised. Familiar applications of the lever — crowbar, poker, 

 scissors, tire tongs, weighing machines. 



Determine the capacity of a bottle by weighing the water it will hold ; find the 

 weight of other liquids — milk, mixtures of milk and water, skimmed milk and 

 cream that till the same bottle, and hence calculate the weight of unit volumes of 

 these liquids. Weight of unit volume a means of testing quality or adulteration 

 of materals. Eeasons why the authorities are so particular as to the milk-supply; 

 milk the only food of very young children and any removal of cream or addition 

 of water would seriously atiect nutrition. 



Weight of unit volume of hot water. Revision of weight of air. Construction 

 of simple air and water pump. 



Determine the weight of one cubic centimetre of air by (a) partially exhausting 



