THE ELEMENTS.] attractions depend upon the same cause, acting in the one case on particles and in tbe other on masses of matter." In 1834 Faraday discovered that the decompositions effected by the voltaic ^current indicate the quantity by weight in which the elements combine, or the weights of the atoms of the atomic theory, thus adding to the probability of the correctness of the supposition that the operations of the same agent are exhibited in both chemical and electrical phenomena. Latterly, the discovery of the action of the copper-zinc couple by Gladstone and Tribe has opened out a new field of electro-chemical research, already productive of important results. To mention, however, the numerous advances that have been made in recent tinies, whether in chemical physics or in chemistry proper especially as regards the constitution and synthesis of the compounds of carbon would be to exceed the scope of the present introductory notice. The reader must, there fore, be referred to the treatises and original memoirs of those whose labours have effected the modern development of chemistry, and have raised it to the high position which it occupies as a science at the present time. (F. H. B.) THE ELEMENTS. The examination of all the various substances met with in nature has led to the discovery of sixty-four different bodies, from which it is impossible by any means now at our disposal to separate simpler substances ; they are consequently termed " elementary or simple bodies," or " elements." It is not asserted that such substances are absolutely simple, or that they may not be found hereafter to yield more than one kind of matter, but merely that so far as our knowledge extends it is so ; indeed, recent spec- troscopic researches favour the impression that some at least of the elements are, perhaps, compounds of simpler bodies. It is the study of the laws which regulate the combina tion of the elements with one another, and to which their compounds are subject in their mutual actions, and of the properties of the elements and of the compounds formed by their union, which constitutes the science of chemistry. The majority of the elements are of comparatively rare occurrence, whilst many of them are extremely rare, being met with only in certain localities. Gold and a few others almost always occur as such, and our atmosphere, we know, consists chiefly of the two elements, oxygen and nitrogen, in the free state; also some others, such as carbon, copper, silver, and sulphur, are occasionally met with in the uncom- bined state, but in general two or more elements are found united. The number of elements of which the materials are made up which principally compose the earth and the plants and animals living upon it is, however, exceedingly small. Thus, plants consist chiefly of carbon, hydrogen, and oxygen, and animals chiefly of these three elements together with nitrogen ; water consists entirely of oxygen and hydrogen. The solid earth is mainly composed of substances such as quartz or silica, chalk or limestone, and various silicates like felspar and clay, the elements which are the chief constituents of these substances being oxygen, silicon, carbon, calcium, magnesium, aluminium, iron, and potassium. The only elements which appear to be absolutely essential to vegetable or animal life are carbon, oxygen, hydrogen, nitrogen, sulphur, phosphorus, calcium, iron, potas sium, sodium, magnesium, silicon, and chlorine ; and the remainder are to us, so to speak, merely of artificial value. Four of the elements chlorine, hydrogen, nitrogen, and oxygen are gases ; and fluorine, which is not known with certainty in the free state, is probably also a gas ; two are liquid at ordinary atmospheric temperatures, viz., mercury and bromine ; and the element gallium, recently discovered in certain zinc ores, but as yet obtained in only very small 467 quantities, is also said to be a liquid. The remaining elements are solids. The following is a list of the elements now known, arranged in alphabetical order. The most important ele ments are distinguished in the table by capitals ; whilst those which at present are of slight importance, on account of their rare occurrence, or of our insufficient knowledge of their properties, are printed in italics. Name of Element. Symbol. Atomic Weight. ALUMINIUM AJ 27-3 Antimony Sb (Stibium) 122 Arsenic As 74-9 Barium Ba 136-8 Bismuth Bi 207-5 Boron B 11 BROMINE Br 79-75 Cadmium Cd 111-6 Ccesium Cs 132-7 CALCIUM Ca 39-9 CARBON C 11-97 Cerium Ce 141 CHLORINE Cl 35-36 Chromium Cr 52-4 Cobalt Co 58-6 Coi PER Cu 63-3 Didymium Di 147 Erbium Er (?)!70-5 Fluorine F 19-1 Gallium Ghicinum G 9-3 Gold Au (Aurum) 196-2 HYDROGEN H 1 Indium In 113-4 IODINE I 126-53 Iridium Ir 196-7 IRON Fe (Ferrum) 55-9 Lanthanum La 139 LEAD Pb (Plumbum) 206-4 Lithium Li 7-01 Magnesium Mg 23-94 Manganese Mn 54-8 MERCURY Molybdenum Kg (Hydrargyrum) Mo 199-8 95-8 Nickel Ni 58-6 Niobium Nb 94 NITROGEN N 14-01 Osmium Os 198-6 OXYGEN
15-96 Palladium Pd 106-2 PHOSPHORUS P 30-96 Platinum Pt 196-7 POTASSIUM K (Kalium) 39-04 Rhodium Ro 104-1 Rubidium Kb 85-2 Ruthenium Eu 103-5 Selenium Se 79 SILICON- Si 28 SILVER Ag (Argentum) 107-66 SODIUM Na (Natrium) 23 Strontium Sr 87-2 SULPHUR S 31-98 Tantalum Ta 182 Tellurium Te 128 Thallium Tl 203-64 Thorium Th (1)178-5 TIN Sn (Staunum) 117-8 Titanium Ti 48 Tungsten W (Wolfram) 184 Uranium U (?)180 Vanadium V 51-2 Yttrium Y (?) 89-5 ZINC Zn 64-9 Zirconium Zr 90 Laws of Combination ly Weight and Volume Their ex planation by the Atomic Theory Determination of the relative Weights of Atoms. The proportions in which elements unite together are definite and constant, a given compound always consisting
of the same elements united in the same proportions.
