from it in the bailiwick of Gibichenstein, for four years, at the annual rent of a barrel of good refined saltpetre. On the same conditions, bishop Ernest, in 1477, let to some one for his lifetime the collection of the saltpetre. In 1544, a certain person obtained the collection of saltpetre from two heaps of rubbish before the gates at Halle. The magistrates of Halle also in 1545 had a saltpetre-work and a powder-mill In the year 1560, John VI., archbishop of Triers, gave to some one permission to search for and dig up saltpetre. In 1583, the saltpetre regale was confirmed by a Brandenburg decree as a thing long known, and the case was the same with a Hessian of the year 1589.

It is very probable that this example was soon followed by most sovereigns; but even if they had collected and scraped together the nitrous incrustation of all the walls in Europe, they certainly would not have found a quantity of saltpetre sufficient for the gunpowder used in the numerous wars which took place, had not a much greater supply been obtained from India, and particularly from Patna. I do not know whether the Portuguese brought this article to Europe; but that it was imported at a very early period by the Dutch is proved by the oldest ladings of their return ships; and they at length found means to appropriate this branch of trade so entirely to themselves, that the other Europeans for a long time could not obtain any saltpetre in India.

In the seventeenth century, when chemistry began to be studied with more care and attention in Europe, and particularly in Germany, and the component parts and production of saltpetre became better known, many conceived the idea of improving the methods of obtaining it in Europe so much, that it might be possible to dispense with the Indian saltpetre, and flattered themselves with the hopes of thence deriving great advantages. Some proposed to fill tubes with putrifiable substances and earth capable of fixing of the nitric acid; others preferred building vaults of these substances, and Glauber recommended the filling of pits with them. The proposal, however, which met with the greatest approbation was that of building walls of them. Through a confidence in this idea, towns and villages were compelled to erect and maintain a certain number of saltpetre walls, under the most gracious promise that the collectors of saltpetre should not

longer be allowed to spoil private dwellings, or render them unhealthful.

But experience has shown that all the means and coercive measures hitherto employed have rendered the European saltpetre much dearer than that obtained by commerce from Bengal. This will be readily comprehended, when it is known that earth richly impregnated with saltpetre abounds in India, and that it may be extracted by lixiviation without any addition, and brought to crystallize in that warm climate without the aid of fire; that the price of labour there is exceedingly low; that this salt is brought from India instea! of ballast by all the commercial nations of Europe, where the competition of the sellers prevents the price from ever being extravagantly high, while the preparation of it in Europe, in consequence of the still increasing price of labour, fuel and ashes, is always becoming dearer. This regale will at length be everywhere scouted. In the duchy of Wurtemberg and the Prussian states, where it was most rigidly enforced, in consequence of an urgent representation from the States it was abolished in 1798; but in both countries an indemnification was given to government for the loss. The case also has been the same in Sweden'. In the duchy of Brunswick it was soon suffered to drop; but in the electoral dominions it never was introduced.

[The greater part of our nitre is derived from Bengal, where, as in Egypt, Persia, Spain, &c., it exists in the soil. It is separated by lixiviation and crystallization. In France, Sweden and some other countries it is prepared artificially in nitre-beds. These are formed of various animal matters, mixed with lime or mortar-rubbish; the mixture is watered and stirred occasionally, and allowed to remain for a considerable time. The whole is then lixiviated and decomposed by carbonate of potash. The nitre is then separated and purified by crystallization. In some cases woodashes are mixed with the animal matters; the decomposition with potash is then unnecessary.

[The celebrated chemist Baron Berzelius, professor at Stockholm, states in his Manual of Chemistry (edit. 1835, vol. iv. p. 86), that every possessor of land in Sweden is still compelled to deliver a certain quantity of saltpetre yearly to the state, and gives directions for testing its goodness.]

It is a question whether the nitric acid in the nitre arises from the nitrogen of the atmosphere or that in the animal matters. Dr. Davy has found nitre in a cave at Ceylon, where no nitrogenous matter was present; and in some parts of India, Spain, and some other countries, at a distance from all habitations, immense quantities of nitre are reproduced in soils which have been washed the year before. Nitre is directly brought into this country from Calcutta and Madras, in bags containing from 150 lbs. to 175 lbs. each. From 200,000 cwts. to 250,000 cwts. are annually imported into the United Kingdom.

In making gunpowder, the components, the sulphur, nitre, and charcoal should be as pure as possible, and reduced to the finest possible powder; they are sifted and mixed in the proper proportions. The mixture is then made into a cake with water, and ground between calcareous millstones. It is then granulated through sieves in another mill, and again sifted. It is then polished and hardened by revolving rapidly in a cask, and finally dried. The proportions of the constituents vary in different countries; at Waltham Abbey they are seventy-five nitre, fifteen charcoal and ten sulphur. The quantity of gunpowder consumed in this country is enormous; moreover, 4,000,000 lbs. are annually exported, the greater part of which is sent to the western coast of Africa.

The force of the explosion of gunpowder is owing to the sudden disengagement of gaseous products; these consist of nitrogen, carbonic oxide, carbonic acid, and sulphurous acid gases; and their volume has been calculated to amount to 2000 times the bulk of the powder.]

BOOK-CENSORS.

"ON account of the great ease," says M. Putter, "with which, after the invention of printing, copies of books could be multiplied and dispersed, it was necessary that some means

should be devised to prevent a bad use from being made of this art, and to guard against its being employed to the prejudice of either religion or good morals, or to the injury of states. For this reason it was everywhere laid down as a general maxim, that no one should be allowed to establish a printing office at pleasure, but by the permission and under the inspection of government; and that no work should be suffered to go to press until it had been examined by a censor appointed for that purpose, or declared by a particular order to be of a harmless nature1."

Many centuries however before the invention of printing, books were forbidden by different governments, and even condemned to the flames. A variety of proofs can be produced that this was the case among both the ancient Greeks and Romans. At Athens the works of Protagoras were prohibited; and all the copies of them which could be collected were burnt by the public crier 2. At Rome the writings of Numa, which had been found in his grave, were, by order of the senate, condemned to the fire, because they were contrary to the religion which he had introduced. As the populace at Rome were, in times of public calamity, more addicted to superstition than seemed proper to the government, an order was issued that all superstitious and astrological books should be delivered into the hands of the prætor. This order was often repeated; and the emperor Augustus caused more than two thousand of these books to be burnt at one time. Under the same emperor the satirical works of Labienus were condemned to the fire, which was the first instance of this nature; and it is related as something singular, that a few years after the writings of the person who had been the cause of the order for that purpose shared the like fate, and were also publicly burnt. (In a manner some 1 Der Büchernachdruck nach ächten Grundsätzen des Rechts geprüft. 1774, 4to.

2 Diogenes Laert. lib. ix. 52.-Cicero de Nat. Deor. lib. i. cap. 23.Lactantius De Ira, ix. 2.-Eusebius De Præparatione Evang. xiv. p. 19. -Minucius Felix, viii. 13.

Livius, lib. xl. c. 29.-Plin. xiii. 13.-Plutarchus in Vita Numæ.Lactantius de Falsa Relig. i. 25, 5.-Valer. Max. i. cap. 1, 12.

Sueton. lib. ii. cap. 31.

5 The whole circumstance is related by Seneca the rhetorician, in the Introduction to the fifth, or, as others reckon, the tenth book of his Controversiæ.

VOL. II.

2 L

what similar the works of Ben. Arias Montanus, who as sisted to make the first catalogue of prohibited books in the Netherlands, were afterwards inserted in a catalogue of the same kind). The burning of these works having induced Cassius Severus to say, in a sneering manner, that it would be necessary to burn him alive, as he had got by heart the writings of his friend Labienus, this expression gave rise to a law of Augustus against abusive writings'. When Cremotius Cordus, in his History, called C. Cassius the last of the Romans, the senate, in order to flatter Tiberius, caused the book to be burnt; but a number of copies were saved by being concealed. Antiochus Epiphanes caused the books of the Jews to be burnt; and in the first centuries of our æra the books of the Christians were treated with equal severity, of which Arnobius bitterly complains. We are told by Eusebius, that Diocletian caused the sacred Scriptures to be burnt. After the spreading of the Christian religion the clergy exercised against books that were either unfavourable or disagreeable to them, the same severity which they had censured in the heathens as foolish and prejudicial to their own cause. Thus were the writings of Arius condemned to the flames at the council of Nice; and Constantine threatened with the punishment of death those who should conceal them". The clergy assembled at the council of Ephesus requested the emperor Theodosius II. to cause the works of Nestorius to be burnt; and this desire was complied with 7. The writings of Eutyches shared the like fate at the council of Chalcedon; and it would not be difficult to collect examples ́of the same kind from each of the following centuries.

We have instances also that, many centuries prior to the invention of printing, authors submitted their works, before they were published, to the judgement of their superiors. This was done principally by the clergy; partly to secure themselves from censure or punishment, and partly to show their respect to the pope or to bishops. It however does not

Taciti Annal. lib. i. c. 72. Bayle, in his Dictionary, has endeavoured to clear up some doubts respecting the history of Cassius and Labienus. See the article Cassius. 2 Tacit. Annal. lib. iv. cap. 35. 4 Adversus Gentes, lib. iii.

• Maccab. ii.

Hist. Eccles. 1. viii. cap. 2. Suidas says the same.

• Socrates, lib. i. cap. 6.

7 Digestor. lib. x. tit. 2, 4,1.