applied knowledge. An invention is usually a combination and application to some desired purpose, of scientific truths which have been previously discovered. When Oersted first observed a magnetic needle move by means of a current of electricity, he made a scientific discovery; but when Wheatstone and Cooke applied Oersted's discovery in their telegraph from Paddington to Slough, they made an invention. The success of the electro-plating process was dependent upon knowledge previously discovered. Mr. Wright, a surgeon in Birmingham, was led to the invention of the use of cyanide of potassium in electro-plating and gilding, by reading in Scheele's "Chemical Essay" (p.p. 405 and 406), that "if after these calces" (i.e., the cyanides of gold and silver) "have been precipitated, a sufficient quantity of precipitating liquor be added, in order to redissolve them, the solution remains clear in the open air, and in this state the ærial acid" (i.e., carbonic acid of the air) "does not reprecipitate the metallic calx."
Immediately a discovery is effected it is made public, and is afterwards incorporated in the ordinary text books of science, ready for the use of inventors; and in this way such books have become filled with valuable knowledge acquired by researches in past times. All this knowledge (which has cost millions of pounds and a vast amount of intellect and labour) has been given by its discoverers freely to the nation. Some idea of the number of scientific
researches which have been made since the year 1800, may be obtained from the fact, that a mere list of their titles, with the names of the authors, occupies eight large quarto volumes, of about one thousand pages each, compiled and published at a cost of about ten thousand pounds, by the British Government and the Royal Society.
In discovery we search for new phenomena, their causes and relations; in invention we seek to produce new effects, or to produce known effects in an improved manner. The objects of the scientific discoverer are, new truth and greater accuracy; whereas those of the inventor, are increased usefulness and economy of results. The ancients classed inventors with the gods, because they considered them great benefactors to the human race. Discoverers may properly be viewed as priests and prophets of truth, because they both reveal new knowledge to mankind, and predict with certainty coming events.
A man cannot usually invent an improvement unless he possesses scientific knowledge, and, for that knowledge he must in nearly all cases resort to a scientific book or teacher. The great practical value of new scientific knowledge is proved by the fact, that when scientific discoveries are published, there are numerous inventors and practical men, who immediately endeavour to apply them to useful purposes. Since the first application of coal-tar to the production of dyes, every discovery in that
branch of chemistry has been closely watched for a similar purpose.
A complete account of the growth and development of scientific discoveries and inventions would form an extensive history, and would include numerous instances of experiments attended by results which, sooner or later, affected all mankind. Take that of phosphorus, for example. The first evidence of the existence of that substance was obtained by the Saracens in the eighth century. Achild Bechil distilled a powdered mixture of charcoal, clay, lime, and dried extract of urine, and obtained a substance which shone in the dark "like a good moon;" that substance was phosphorus. The discovery contained in the results of that little dirty and stinking experiment was the germ or seed of all the subsequent developments and applications of phosphorus. About the year 1669 Bechil's experiment was further developed by Brandt, a merchant of Hamburg, and the publication of the wonderful properties of the substance produced a great sensation in his fellow-citizens. "There was then cried nothing but triumph and victory among the chymists. Those good people erected already in their thoughts so many hospitals and poor-houses that no beggar should more molest any man in the streets, made great legacies, and pious causes, and what not else." "Besides, the other alchymists did encourage him yet more, and desisted not to make him believe how this was the same fiery ghost of
Moses that in the beginning moved upon the water, yea, his splendid shining face: the fiery pillar in the desert, that secret fire of the altar wherewith Moses burned the golden calf before he strewed it upon the fire and made it potable."
The experiment of Brandt was repeated by Kunckel before the courts of Saxony and Brandenburg, although it was not a very delicate or agreeable exhibition, "because the anctuous and daubing oyliness was not yet accurately separated from it, and without doubt it was very stinking." Brandt's process was further developed by Boyle, and published in the Philosophical Transactions of the Royal Society, in the year 1692-3; and phosphorus was afterwards obtained in larger quantity and in a purer state by Hanckwitz, a chemist in Southampton Street, Strand, and sold by him at three pounds sterling per ounce. Its price at present is less than three shillings per pound.
Margraaf, Fourcroy, Vauquelin, and Dr. Slare also extended our knowledge of the substance; Gahn, in 1769, made the important discovery of phosphorus in bones, and Scheele immediately devised the process now in use by our manufacturers for extracting it from that substance. The commencement of the use of phosphorus for the purpose of getting a light occurred about the year 1803, but it was not until the year 1833 that the invention of phosphorus matches became commercially successful. The use of such matches is now universal, and it has