and, having corked it, place it outside of the window exposed to frost-in the morning the glass will be found broken, and it will be seen that the ice is larger than the original water.

On one occasion, Major Williams tried the following experiment at Quebec :-Having fitted a plug weighing 3lb. into a bomb-shell filled with water, he exposed it to the action of the frost. The expansion of the contents in freezing projected the plug to a considerable distance; in screwing in the plug afterwards, the shell was actually burst. May we not, then, say, 66 Nature, nature, who can stop thy course!"

QUESTIONS.

85. Do all bodies contract by cold?

86. Why is bismuth used in making small type-metal? 87. What design had the Creator in view in ordaining that water should expand in freezing?

88. When water freezes in pipes and crevices of rocks does it exert any force?

89. Describe the experiment which was tried in Quebec by Major Williams?

31. It would be advisable to try the following (experiment 14) for the purpose of showing that water also expands by heat:-Pour water into an oil-flask* to within an inch of the top-on holding

*

Young persons who are desirous of performing experiments, should collect the empty oil-flasks at home, and have them washed with potash-they will be found extremely useful.

it over the fire the contents will overflow considerably below the boiling point. This experiment exhibited to a servant would show the necessity for not filling the kettle, as is usually done.

32. While the flask is in the hands of the operator it would not be a loss of time to try experiment 15. Boil a tea-spoonful of water in the flask-when full of steam, which occupies about 1728 times the space of the original water, invert it suddenly in a basin of cold water; the heat being abstracted from the confined steam, in returning to the state of water it contracts to its original dimensions, leaving a vacuum in the flask; the atmosphere then pressing on the water in the basin will force it up into the flask with considerable velocity, and in many cases will crack the flask. This experiment, presented accidentally to the gifted mind of Captain Savery, led him to construct the first steam-engine that was brought into operation in 1698.

QUESTIONS.

90. You have said that water expands when frozen-does it also expand when heated?

91. To what extent does water expand when it is converted into steam?

92. When a flask filled with steam is suddenly immersed in cold water, why is it immediately filled from below?

33. We will close the subject of expansion and contraction by directing attention to air, which is also subject to this law.

Experiment 16.-Invert in water an oil-flask half filled with the liquid; pour hot water on the flask, when it will be found that the expansion of the confined air will expel the water. The converse of this

is equally interesting. Having inverted the flask in water, pour some sulphuric ether over it; by its evaporation (vide exper. 10) the confined air will be robbed of a portion of its heat, and, contracting into a smaller space, will allow the atmospheric pressure to force the water into the flask. Upon the principle of air expanding and contracting, air thermometers are constructed.

Experiment 17.-Hold a light paper balloon over ignited spirit of wine; the heat will expel such a considerable portion of the air that the balloon will ascend from the following cause:-Heat is imponderable, that is, has no weight; when it expels a part of the air, a ponderable agent, the remaining portion, mixed with the heat, occupies the cavity of the balloon-and thus becoming lighter than an equal volume of the external atmosphere, it ascends upon the same principle that a cork floats in water.

QUESTIONS.

93. Give an illustration of the expansion and contraction of air?

94. When you ignite spirit of wine under a paper balloon, why does it ascend?

34. We have now to consider the transmission of heat by conduction. It can easily be proved that heated bodies part with the overplus of the caloric to surrounding agents until a balance or equilibrium is established; but it has been wisely planned by the Creator that all substances should not have the same power of abstracting it from the heated bodies. On this account they are divided into good and bad conductors, the process being termed conduction. Solids possess this power in a greater degree than liquids or gases. Among solids, metals are the best. Among bad conductors we find glass, baked wood, charcoal, sand, hair, feathers, and fur. This can be made evident to a child, by holding rods of wood and iron over the flame of a lamp-the wood, while red hot at one end, can still be held by the other extremity; this will not be the case, however, with the iron-proving the unequal conducting powers of these bodies. A similar case will be seen in the construction of a teapot the handle being a bad conductor of heat.

35. From a knowledge of these facts, we cannot fail to be struck with astonishment at the inimitable skill with which the Creator has protected animals. We have said that hair, feathers, and fur are among the worst conductors of heat: if, therefore, we cover a heated body with any of them, its temperature will be preserved from the external atmosphere; and it is worthy of observation, that in proportion as the climate is colder, the non-conducting cover is increased, as we see by comparing the few hairs on the elephant

QUESTIONS.

102. Why are the eggs of the turtle hatched by being buried in sand ?

103. Why do thick glass vessels split more easily by heat than thin ones?

104. Is water a non-conductor of heat?

THE ELEMENTS,

OR SIMPLE BODIES OF WHICH OUR GLOBE IS COMPOSED.

39. When we look around us and behold the endless variety of nature's productions, it appears impossible, at a superficial glance, to ascertain the simple bodies or elements which enter into their compositions. By the unwearied exertions, however, of the human mind, we are led to suppose that about fifty-five elements were employed by nature in constructing the animal, vegetable, and mineral kingdoms. This is at present the received opinion; subsequent discoveries may prove that they are more or less. The ancients supposed that the elements of nature were fire, air, earth, and water: modern chemistry proves that the three latter are compound bodies; of the real nature of fire or caloric nothing as yet has been determined. We find traces of the ancient opinion in poetry and general conversation. Thus