1830.] The Progress of Physical Discovery. 



strument gives a sound, it is the seat of molecular motion. In every 

 case of vibration the molecules move in a straight line ; and however the 

 system of bodies may be disposed, all the molecules move in right lines 

 parallel to each other, and to the right line by which the bow is con- 

 duced, which leads us to consider such a system as forming but a single 

 body, since the molecules all move in the same manner. But when we 

 reflect that each of these molecules is, in fact, a world of itself, and sub- 

 jected to laws as peculiar to itself as those which are assigned to the 

 several planets in their spheres, we cannot but be struck with the man- 

 ner in which the whole system of nature is, as it were, concentrated into 

 one point, and reflected in the properties of every one of its most minute 

 elementary particles. 



In 1825 a new acid was detected by M. Braconnot, which pervades 

 generally the vegetable kingdom, particularly bulbous roots, fruits, and 

 grains. It is called pectic, and has the property of turning into jelly a 

 large mass of sugared water, though used in a very small portion. 

 Another vegetable alkali was found by Brandes in narcotic plants, and an 

 acid called pariglini, in Sarsaparilla, by Palletta of Naples. In this and 

 the preceding year, Sir Humphrey Davy made a most useful applica- 

 tion of his observations on electricity, by his method of preserving the 

 copper sheathing of ships from corrosion by the introduction of small 

 pieces of zinc or iron, whereby the copper is changed from a positive to 

 a negative state of electricity. M. Arago, in his experiments on the 

 thermometer., found, that in no time or place will a thermometer, raised 

 two or three metres above the sun, and sheltered from reverberation, 

 reach the 37th degree of Reaumur, (115 of Fahrenheit); that at open 

 sea, at no time or place, will the temperature of the air exceed 24 of 

 Reaumur, (86 Fahr.) ; that the highest degree of cold observed on our 

 globe, with a thermometer suspended in the air, is 40 Reaumur, (56 

 below zero, Fahr.) ; and that salt water, at whatever latitude or season, 

 never takes a higher temperature than 24 Reaumur, (86 Fahr.) 



M. Freycinet's observations on the pendulum, reported to the French 

 academy on his return from his voyage round the globe in 1826, present 

 the following result : That the general flattening of the globe is sensibly 

 greater than that which had been deduced from the measures of the 

 meridian, or the theory of the moon (a remark which has since been 

 confirmed by Captain Sabine) ; that there is no reason to suppose that 

 the northern and southern hemispheres have different degrees of flatten- 

 ing ; and that, in some parts of the globe, as in the Isle of France, local 

 circumstances produce considerable irregularities in the oscillations of 

 the pendulum. A new acid was in this year discovered by that perse- 

 vering chemist, Mr. Farraday, called sulfo-naphtalic, from its being ob- 

 tained by the mixture of naphtaline, disembarrassed of naphta by sub- 

 limation, with three or four times its weight of cold sulphuric acid. A 

 mineral substance, that had been some years ago found in the salt-works 

 of Espartines, near Madrid, by a Spanish manufacturer, named Rodas, 

 was now ascertained by M. Casaseca to consist of sulphate of soda, with 

 a very small portion of sub- carbonate of soda, and was assigned the 

 name of thenardite. The substance called brome was now first detected 

 in sea water by M. Balard. It is liquid under the ordinary temperature 

 of the atmosphere ; its colour in mass is from a red brown to a red 

 hyacinth ; and that of its vapour is very like the colour of nitrous acid. 

 It is very volatile, and its odour is strong, and much resembles that of 



