AND OF THE PHYSICAI SCIENCES. 



1] 



NATURAL PHILOSOPHY. 



A FEW ELEMENTARY TRUTHS REGARDING ELECTRICITY. 



There is no department of science which, at the present day, is extend- 

 ing its boundaries more rapidly and widely than Electricily, and that to the 

 astonishment and delight of all who are watching its progress. Some 

 particulars regarding it are somewhat obscure and difficult of apprehension, 

 but the great majority are quite level to common capacities, and excite 

 the liveliest attention to their results, at once familiar, and, many of them, 

 beyond conception, remarkable and grand. We hope frequently to bring 

 some of these novelties under the attention of our readers; and as we 

 would " begin with the beginning," we shall endeavour on the present 

 occasion to propound some of the elemental truths of the science, in a 

 manner that will be level nearly to every capacity. Our motive will, we 

 are confident, command the forbearance of the more accomplished stu- 

 dent. 



If a smooth glass tube, or a stick of sealing-wax, be rubbed on the sleeve 

 of the coat, or with a piece of dry flannel, it will be found to have acquired 

 from this friction a new property, which will be exhibited by holding the 

 newly rubbed body over small shreds of paper, or any other light article 

 placed on the table, which will be immediately affected. This property 

 was originally named electricity, from being first observed in amber, the 

 electron of the Greeks. About a hundred years ago, it was discovered 

 that there were two different kinds of electricity, occasioned by the differ- 

 ent methods in which it was excited. When produced by glass, hair, 

 wool, and many other bodies, it was called vitreous or positive ; when 

 produced by resinous substances, such as wax, and by amber, silk, &c, it 

 was called resinous or negative ; and the distinguishing character of these 

 two electricities is, that a body with positive electricity repels all bodies 

 with positive electricity ; and a body with negative electricity repels all 

 bodies with negative electricity ; while, at the same time, each mutually 

 attracts the other. Hence, two electrified silk threads repel each other, 

 as do also two electrified woollen threads, but an electrified silk will at- 

 tract an electrified woollen thread. Intimately connected with this pro- 

 perty of attraction and repulsion is another not less interesting, namely, 

 that of exciting light, not unfrequently in the form of sparks, as is often 

 seen in separating certain silk and woollen stockings which have been 

 worn. A variety of suitable instruments, known under the name of 

 electrical machines, were speedily invented for exciting this agent in large 

 quantities, and from these the electric spark may be procured in great 

 brilliancy. Ere long, another apparatus was devised, not for exciting the 

 spark, but for retaining and accumulating the electricity when formed. 

 The most celebrated of these is the Leyden phial, or electric jar, whose 

 retaining property depends upon the fact that certain substances are non- 

 conductors ; for when a body highly electrified is touched with a piece 

 of glass, its peculiar property suffers no change, but if touched with a 

 piece of metal, it is instantly deprived of all its electricity ; hence the 

 glass and the metal possess different properties, the former being incapable, 

 and the latter capable, of carrying off' electricity ; and hence the metal is 

 said to be a conductor, and the glass a non-conductor of electricity. Many 

 other substances belong to each of these classes ; and, accordingly, the 

 electricity of a body, speedily dissipated in the open air, may, by simple 

 contrivances, be long retained in the Leyden jar; and a number of these 

 jars being collected, and combined together in suitable arrangement, form 

 the electric battery, in which numerous sparks may be collected, and 

 powerful shocks may be communicated. It is long since the phenomena 

 of this electricity were compared and identified with those exhibited by 

 that of the atmosphere when serene, and when they appear with new 

 splendour in the terrific grandeur of thunder and lightning. Mr Dalebard, 

 at the instigation of Count Buffon, erected near Paris an iron rod upon 

 three long poles, insulated by glass feet and silken threads, whence on 

 the 10th of May 1 752 sparks were elicited by many astonished observers 

 with a crackling noise. It was in June of the same year that the cele- 

 brated Franklin obtained similar results from his silken kite, by its means 

 drawing the lightning down from the clouds ; and immediately afterwards 

 the same effects were every where procured. Under arrangements made 

 with a kite by Romas, flashes of fire a foot long, and three inches wide, 

 were received with a noise audible at the distance of 500 feet, and straws 

 three feet from the conductor were made to dance upon the ground. 



At the same time it is not to be forgotten that there are many other 

 excitants of electricity besides friction, of which we shall enumerate a 

 few. One of these is heat (Thermo-electricity), the effects of which are 

 strikingly exhibited in many minerals and salts, and in metallic bodies, as 

 by raising the temperature of one end of a plate of silver, while the other is 

 retained at the temperature of the surrounding air: Another is galvanism 

 (Voltaic electricity); and a third magnetism (Magnetic electricity). On 

 these we must not dwell. But, moreover, even simple pressure induces 

 electricity, as when a piece of cork is pressed against a piece of Indian 

 rubber ; so does a change of form, as in the melting and cooling of resinous 

 bodies ; as likewise do the common processes of evaporation and combus- 

 ion, and especially that peculiar chemical action which occurs in every 



instance of chemical union and decomposition. From all this it cannot 

 but follow as a necessary consequence that electricity is produced abun- 

 dantly in the complicated processes which are ever going forward in ani- 

 mated nature. The recent experiments of M. Pouillet have clearly de- 

 monstrated this in vegetation, and led to the conclusion that a vegetating 

 surface of 100 square yards in extent produces in a day more electricity 

 (negative) than would be sufficient to charge the strongest battery ; and 

 electricity resulting from animal life, may with all safety be inferred to be 

 still more copious and powerful. 



The phenomena of attraction and repulsion, proceeding from bodies in 

 different states of electricity, is admirably exhibited by stockings after they 

 have been worn in a very common fashion, which long ago was well de- 

 scribed by Mr Symmer. This gentleman found the electricity most 

 powerful when a silk and worsted stocking had been worn on the same 

 leg; and was best exhibited by putting the hand between the leg and the 

 stockings, and pulling them off together. The one stocking being thus 

 drawn out of the other, they appeared more or less inflated. Mr 

 Symmer's first trials were accidentally made with black silk stockings, and 

 he was surprised to find that white ones produced no electricity. Two 

 white silk stockings, or two black ones, when put on the same leg and 

 taken off, gave no electrical indications. When a black and a white 

 stocking were put on the same leg, and at the end of ten minutes taken 

 off, they were so much inflated when pulled asunder, that each of them 

 showed the entire shape of the leg, and at the distance of a foot and a 

 half they rushed to meet each other. With worsted stockings, also, no- 

 thing but the combination of black and white produced electricity. When 

 an excited white and black stocking are presented to each other, they 

 attract one another, inclining to each other at the distance of three feet, 

 catching hold of each other within two feet, and at a less distance rush- 

 ing together with surprising violence, becoming as flat as so many folds of 

 silk when they are joined. But what appears most extraordinary is, that 

 when they are separated, and removed to a sufficient distance fiom each 

 other, their electricity does not seem to have been in the least impaired 

 by the shock they had in meeting. They are again inflated, again attract 

 and repel, and are ready to rush together as before. When this experi- 

 ment is performed with two black stockings in one hand, and two white 

 in the other, it exhibits a very curious spectacle; the repulsion of those 

 of the same colour, and the attraction of those of different colours, throws 

 them into an agitation which is not unentertaining, and makes them catch 

 each at that of its opposite colour, at a greater distance than one would 

 expect. When allowed to come together, they all unite in one mass. 

 When separated they resume their former appearance, and admit of the 

 repetition of the experiment as often as you please, till their electricity, 

 gradually wasting, stands in need of being recruited. In the course of his 

 experiments Mr Symmer accidentally threw a stocking out of his hands, 

 and some time afterwards he found it sticking to the paper hangings of 

 the room. They stuck also to the painted pannelling, and often con- 

 tinued for a whole hour suspended upon the hangings. 



HYDROGRAPHY. 



INTERMITTENT BRINE SPRINGS, NEAR KISSINGEN, IN BAVARIA, 



The following is a summary of an able paper read to the Royal Socieh 

 of Edinburgh by that most indefatigable cuJtivator of Science, Professor 

 Forbes. We extract it from the published *' Proceedings" of the So- 

 ciety. The Memoir is published in full in the April Number of the Edin . 

 burgh New Philosophical Journal, and is, of course, still more interesting 

 than the Summary. 



The watering-place of Kissingen is situated about 60 English niilej 

 east of Frankfort. Long before it was frequented for medical purposes, 

 its salt springs were turned to profitable account. Of these there are 

 several, but the one recently enlarged by boring, known under the name 

 of the Runde Brunnen, is much more remarkable than the others, on 

 account of its Copiousness, its Temperature, its discharge of Carbonic 

 Acid Gas in vast quantity, and its extraordinary phenomenon of Inter- 

 mission. 



The spring rises through the new red sandstone, of which the valleys 

 in the neighbourhood of Kissingen are composed, on the left bank of the 

 river Saal, whose course is marked for many miles by the occurrence of 

 mineral springs, and by the discharge of carbonic acid gas. The author 

 supposes its direction to be connected with a line of fissure, and the gas 

 to have its origin in the neighbouring extinct volcanic focus of the 

 Rhongebirge. 



The present spring was bored for in 1822, and the 4-inch shaft was 

 carried to a depth of 323 Bavarian feet from the surface; but at the top 

 it expands into a well eight feet in diameter. At a depth of 156 feet, the 

 water ebbed for the first time, and it has done so since with more or less 

 regularity ; but what is particularly strange is, that this regularity appears 

 to depend in a not very conceivable way upon the action of the pumps 

 which are employed to raise the brine from the shaft for the purpose of 



