a game amongst the Romans, of much the same nature with our chess. The latrunculi were properly the chessmen, called also latrones and calculi. They were made of glass, and distinguished by black and white colours. Sometimes they were made of wax or other convenient substances. Some give the invention of this game to Palamedes when at the siege of Troy: Seneca attributes it to Chilon, one of the seven Greek sages; others honour Pyrrhus with the invention; and others again contend that it is of Persian origin—but is not this Lis de lana caprina? Frequent allusions to this game are met with in the Roman classics, and a little poem was written upon it, addressed to Piso, which some say was the work of Ovid, others of Lucan, in the end of some editions of whose works it is to be found, and to which we refer for a fuller account of the game. This game expresses so well the chance and order of war, that it is, with great appearance of probability, attributed to some military officer as the inventor. One Canius Julius was so exceedingly fond of chess, that after he was sentenced to death by Caligula, he was found playing, but interrupted in his game by a call to execution; he obeyed the summons, but first defied the centurion who brought the fatal order, to bear witness that he had one man upon the board more than his antagonist, that he might not falsely brag of victory when he should be no more.

LATTEN denotes iron plates turned over, of which tea canisters are made.

Plates of iron being prepared of a proper thinness, are smoothed by rubbing them in an acid liquor, as common water made eager with rye. With this liquor they fill certain troughs, and then put in the plates, which they turn once or twice a-day, that they may be equally rusted over. After this they are taken out, and well scour'd with sand; and, to prevent their rusting again, are immediately plunged into pure water, in which they are to be left till the instant they are to be tinned or blanched; the manner of doing which is this: They flux the tin in a large iron crucible, which Latter, has the figure of an oblong pyramid with four faces, of which two opposite ones are less than the two others.

The crucible is heated only from below, its upper part being luted with the furnace all round. The crucible is always deeper than the plates which are to be tinned are long; they always put them in downright, and the tin ought to swim over them; to this purpose artificers of different trades prepare plates of different shapes, though Mr Reaumur thinks them all exceptional. But the Germans use no sort of preparation of the iron to make it receive the tin, more than the keeping it always steeped in water till the time; only when the tin is melted in the crucible, they cover it with a layer of a sort of suet, which is usually two inches thick, and the plate must pass through this before it can come to the melted tin. The first use of this covering is to keep the tin from burning; for if any part should take fire, the suet would soon smother it, and reduce it to its primitive state again. The blanchers say, this suet is a compounded matter. It is indeed of a black colour; but Mr Reaumur supposed this to be only an artifice to make it a secret, and that it is only coloured with soot or the smoke of a chimney: but he found it true so far, that the common unprepared suet was not sufficient; for after several attempts, there was always something wanting to render the success of the operation certain. The whole secret of blanching, therefore, was found to lie in the preparation of this suet; and this at length he discovered to consist only in the first frying and burning it. This simple operation not only gives it the colour, but puts it into a condition to give the iron a disposition to be tinned, which it does surprisingly.

The melted tin must also have a certain degree of heat; for if it is not hot enough, it will not stick to the iron; and if it is too hot, it will cover it with too thin a coat, and the plates will have several colours, as red, blue, and purple, and upon the whole will have a cast of yellow. To prevent this, by knowing when the fire has a proper degree of heat, they might try with small pieces of iron; but, in general, use teaches them to know the degree, and they put in the iron when the tin is at a different standard of heat, according as they would give it a thicker or thinner coat. Sometimes also they give the plates a double layer, as they would have them very thickly covered. This they do by dipping them into the tin when very hot the first time, and when less hot the second. The tin which is to give the second coat must be fresh covered with suet; and that with the common suet, not the prepared.

**Latten Brafs**, plates of milled brafs reduced to different thicknesses, according to the uses they are intended for.

**Lattimo**, in the glas trade, a name for a fine milk-white glas. There are several ways of making it, but the best of all is this: take 400 weight of crystal frit, 65 pounds of calcined tin, and two pounds and a half of prepared manganese; mix these well with the frit, and set them in a pot in a furnace to melt and refine. At the end of 18 hours this will be purified; then cast it into water, purify it again afterwards in the furnace, and make a proof of it. If it be too clear, add 15 pounds more of calcined tin; mix it well with the metal, and let it stand one day to purify; it will then be of a whiteness surpassing even that of snow, and is fit to work into vessels.

**Latus Primarium**, a right line drawn through the vertex of the section of a cone, within the same, and parallel to the base.

**Latus Transversum** of the hyperbola, is the right line between the vertices of the two opposite sections, or that part of their common axis lying between the two opposite cones.

**Lava**, a stream of melted minerals which runs out of the mouths, or bursts out through the sides, of burning mountains, during the time of an eruption. See *Aetna*, Vesuvius, Hecla; and see also Volcano, Geology Index.

The lava at its first discharge is in a state of prodigious ignition, greatly superior to any thing we can have an idea of from the small artificial furnaces made by us. Sir William Hamilton informs us, that the lava of Vesuvius, at the place whence it issued (in the year 1767), "had the appearance of a river of red hot and liquid metal, such as we see in the glass houses, on which were large floating cinders half lighted, and rolling over one another with great precipitation down the side of the mountain, forming on the whole a most beautiful and uncommon cascade."

Now, if we consider the materials of which the lava consists, which undoubtedly are the common matters to be found everywhere in the earth, namely, stones, metallic ores, clay, sand, &c. we shall find that our hottest furnaces would by no means be able to bring them into any degree of fusion; since the materials for glass cannot be melted without a great quantity of very fusible salts, such as alkalies, nitre, &c. mixed along with them. The heat of a volcano must therefore be immense; and besides its heat, it is sometimes attended with a very uncommon circumstance; for Sir William Hamilton informs us, that "the red hot heat of stones thrown up by Vesuvius on the 31st of March 1766, were perfectly transparent;" and the like remark he makes on the vast stream of lava which issued from the same volcano in 1779. This we cannot look upon to be the mere effect of heat; for mere heat with us will not make a solid body transparent; and these stones, we are sure, were not in a state of fusion, or the resistance of the air would have broke them all to pieces, even supposing them, which is very improbable, to have been in that state detached from the rest of the lava. For the transparency, therefore, (according to some authors) we must have recourse to electricity; which in some of our experiments hath the property of rendering opaque bodies transparent*. Indeed it is scarcely possible but the lava and every other matter thrown out by a volcano must be in the highest degree electrical, if the fire itself take its rise from electricity.

The lava, after having once broke out, does not probably constantly continue running from the same vent, but in highly often has intermissions, after which it will burst out electrified sometimes at the same place, and sometimes at another. No real flame ever appears to come from the lava. In the day time its progress is marked by a thick white smoke, from which the light of the red hot matter, being reflected in the night time, makes it appearance like flame. But if, during its progress, it meets with trees or other combustible substances, which it frequently does, a bright flame immediately issues from its