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fers in his work entitled "Eudosia, or a Poem on the Universe:"

All homogeneous fluids, which ascend
To equal heights, and join in equal base,
Balance each other; howsoe'er in form
Of the containing vessel disagreed,
Or in the fluid quantity contain'd.

Emma. What does he mean by the word homogeneous?

Father. Homogeneous fluids are fluids of the same kind. What has been proved with regard to water may be shown to hold with regard to wine, or oil, or any other fluid. But the experiment will not answer if different fluids are made use of, as water and oil together.

CONVERSATION VII.

Of the Hydrostatic Bellows.

FATHER. I think we have made it sufficiently clear that the pressure of fluids of the same kind is always proportional to the area of the base multiplied into the perpendicular height at which the fluid stands, without any regard to the form of the vessel, or the quantity of fluid contained in it.

Emma. I cannot help saying, that it still appears very mysterious to me, that a pint of water, in the narrow vessel (p. 50), should have an equal pressure with the 20 pints in the next vessel. You will not say that one pint weighs as much as the 20.

vided the external pressure is taken

off.

Father. Certainly: I will take off the bladder from this glass. The little images all swim at the top, the air contained in them rendering them rather lighter than the water. Tie little leaden weights to their feet, and they are then pulled down to the bottom of the vessel. I now place the glass under the receiver of the air-pump, and, by exhausting the air from the vessel, that which is within the images, by its elasticity, expands itself, forces out more water, and you see they are ascending to the top, dragging the weights after them. I will let in the air, and the pressure forces the water into the images again, and they descend.

Here is an apple very much shrivelled, which, when placed under the

upon the bottom of the smaller vessel would be much less than that upon the

larger.

Here is another in

strument to show you that a very few ounces of water will lift up and sustain a large weight.

Emma. What is W

the instrument called?

Father. It is made

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like common bellows, only without valves, and writers have given it the name of the hydrostatic bellows. This small tin pipe e op communicates with the inside of the bellows. At present the upper and lower board are kept close to one another, with the weight

w.

The inside of the boards is not

very smooth, so that water may insinuate itself between them: pour this half-pint of water into the tube.

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Emma.

It seems to boil, now you exhaust the air from the re ceiver.

Father. The bubbling is caused by the air endeavouring to escape from the liquor. Let the air in again, and then taste the beer.

Charles. It is flat and dead.
Father.

You see of what importance air is to give to all our liquors their pleasant and brisk flavour, for the same will happen to wine and all other fermented fluids.

Emma.

How is it that the air, when it was re-admitted, did not penetrate the ale again?

Father. It could not insinuate itself into the pores of the beer, because it is the lighter body, and therefore will not descend through the heavier, Besides, it does not follow that it is the same sort of air

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