A preliminary discourse on the study of natural philosophy


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Pàgina 160 - But there still remains the most important case of all, that of nocturnal dew : does the same circumstance exist in this case ? Is it a fact that the object dewed is colder than the air? Certainly not, one would at first be inclined to say ; for what is to make it so? But .... the experiment is easy ; we have only to lay a thermometer in contact with the dewed substance, and hang one at a little distance above it, out of reach of its influence. The experiment has been, therefore, made ; the question...
Pàgina 162 - ... single and perfectly definite new circumstance, and manifesting the effect so rapidly that there is not time for any other material change in the pre-existing circumstances. " It is observed that dew is never copiously deposited in situations much screened from the open sky, and not at all in a cloudy night ; but if the clouds...
Pàgina 158 - Many of the new elements of chemistry have been detected in the investigation of residual phenomena. Thus Arfwedson discovered lithia by perceiving an excess of weight in the sulphate produced from a small portion of what he considered as magnesia present in a mineral he had analyzed.
Pàgina 84 - When Captain Head was travelling across the Pampas of South America, " his guide one day suddenly stopped him, and, pointing high into the air, cried out ' A lion !' Surprised at such an exclamation, accompanied with such an act, he turned up his eyes, and with difficulty perceived, at an immeasurable height, a flight of condors soaring in circles in a particular spot.
Pàgina 287 - geology, in the magnitude and sublimity of the objects of which it treats, undoubtedly ranks, in the scale of the sciences, next to astronomy...
Pàgina 14 - The colours which glitter on a soap-bubble are the immediate consequence of a principle the most important from the variety of phenomena it explains, and the most beautiful, from its simplicity and compendious neatness, in the whole science of optics.
Pàgina 179 - The formulae," says Sir John Herschel,* " which have been empirically deduced for the elasticity of steam (till very recently), and those for the resistance of fluids, and other similar subjects," when relied on beyond the limits of the observations from which they were deduced, " have almost invariably failed to support the theoretical structures which have been erected on them.
Pàgina 25 - ... millions of millions of times ; of yellowness, five hundred and forty-two millions of millions of times ; and of violet, seven hundred and seven millions of millions of times per second.* Do not such things sound more like the ravings of madmen, than the sober conclusions of people in their waking senses...
Pàgina 60 - The combustion of seven bushels of coal would suffice to raise it to the place where it hangs. The great pyramid of Egypt is composed of granite. It is 700 feet in the side of its base, and 500 in perpendicular height, and stands on eleven acres of ground. Its weight is, therefore, 12,760 millions of pounds, at a medium height of 125 feet ; consequently it would be raised by the effort of about 630 chaldrons of coal — a quantity consumed in some foundries in a week.
Pàgina 53 - Czar/ a man would be ashamed to follow Socrates. Sir, the impression is universal ; yet it is strange. As to the sailor, when you look down from the quarter-deck to the space below, you see the utmost extremity of human misery ; such crowding, such filth, such stench !" BOSWELL. "Yet sailors are happy.

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