Archimedes Project

126

The list of Sir Jonas's works, as far as I have seen them, are the following:

1. The New System of Mathematics; above mentioned, in 2 vols 4to, 1681.

2. Arithmetic in two books, viz, Vulgar Arithmetic and Algebra. To which are added two Treatises, the one A new Contemplation Geometrical, upon the Oval Figure called the Ellipsis; the other, The two first books of Mydorgius, his Conical Sections analized &c. 8vo, 1660.

3. A Mathematical Compendium; or Useful Practices in Arithmetic, Geometry, and Astronomy, Geography and Navigation, &c, &c. 12mo, 4th edition in 1705.

4. A General Treatise of Artillery: or, Great Ordnance, Written in Italian by Tomaso Moretii of Brescia. Translated into English, with notes thereupon, and some additions out of French for Sea-Gunners. By Sir Jonas Moore, Kt. 8vo, 1683.

MORTALITY. Bills of Mortality, are accounts or registers specifying the numbers born, and buried, and sometimes married, in any town, parish, or district. These are of great use, not only in the doctrine of Life Annuities, but in shewing the degrees of healthiness and prolificness, with the progress of population in the places where they are kept. It is therefore much to be wished that such accounts had always been correctly kept in every kingdom, and regularly published at the end of every year. We should then have had under inspection the comparative strength of every kingdom, as far as it depends on the number of inhabitants, and its increase or decrease at different periods.

Such accounts are rendered still more useful, when they include the ages of the dead, and the distempers of which they have died. In this case they convey some of the most important instructions, by furnishing the means of ascertaining the law which governs the waste of human life, the values of annuities dependent on the continuance of any lives, or any survivorships between them, and the favourableness or unfavourableness of different situations to the duration of human life.

There are but few registers of this kind; nor has this subject, though so interesting to mankind, ever engaged much attention till lately. Indeed, bills of Mortality for the several parishes of the city of London have been kept from the year 1592, with little interruption; and a very ample account of them has been published down to the year 1759, by Dr. Birch, in a large 4to vol. which is perhaps the fullest work of the kind extant; containing besides the bills of Mortality, with the diseases and casualties, several other valuable tracts on the subject of them, and on political arithmetic, by several other authors, as Capt. John Graunt, F. R. S.; Sir William Petty, F. R. S.; Corbyn Morris, Esq. F. R. S.; and J. P. Esq. F. R. S.; the whole forming a valuable repository of materials; and it would be well if a continuation were published down to the present time, and so continued from time to time.

Bills containing the ages of the dead, were long since published for the town of Breslaw in Silesia. It is well known what use has been made of these by Dr. Halley, and after him by Mr. De Moivre. A table of the probabilities of the duration of human life at every age, deduced from them by Dr. Halley, was published in the Philos. Trans. vol. 17, and has been inserted in this work under the article Life-Annuities; which is the first table of this kind that has been published. Since the publication of this table, similar bills have been established in many other places, in England, Germany, Switzerland, France, Holland, &c, but most especially in Sweden; the results of some of which may be seen in the large comparative table of the duration of life, under the article Life-Annuities, in this work.

MORTAR

, or Mortar-Piece, a short piece of ordnance, thick and wide, proper for throwing bombshells, carcases, stones, grape-shot, &c.

It is thought that the use of Mortars is older than that of cannon: for they were employed in the wars of Italy, to throw balls of red-hot iron, and stones, long before the invention of shells: and it is generally believed that the Germans were the first inventors. The practice of throwing red-hot balls out of Mortars, was first practised at the siege of Stralfund in 1675, by the elector of Brandenburg; though some say, in 1653, at the siege of Bremen.

Mortars are made either of brass or iron, and it is usual to distinguish them by the diameter of the bore; as, the 13 inch, the 10 inch, or the 8 inch Mortar: there are some of a smaller sort, as Coehorns of 4.6 inches, and Royals of 5.8 inches in diameter. As to the larger sizes, as 18 inches, &c, they are now disused by the English, as well as most other European nations. For the circumstances reiating to Mortars, see Muller's Artillery.

Coeborn Mortar, a small kind of one, invented by the celebrated engineer baron Coehorn, to throw small shells or grenades. These Mortars are often fixed, to the number of a dozen, on a block of oak, at the elevation of 45°.

MOTION

, or Local Motion, is a continued and successive change of place. Borelli defines it, the successive passage of a body from one place to another, in a determinate time, by becoming successively contiguous to all the parts of the intermediate space.

Motion is considered as of various kinds; as Natural, Violent, Absolute and Relative, &c, &c.

Natural Motion, is that which has its principle, or actuating force, within the moving body. Such is that of a stone falling towards the earth. And

Violent Motion, is that whose principle is without, and against which the moving body makes a resistance. Such is that of a stone thrown upwards, or of a ball shot off from a gun, &c.

Motion is again divided into Absolute and Relative.

Absolute Motion, is the change of absolute place, in any moving body, considered independently of any other motion; whose celerity therefore will be measured by the quantity of absolute space which the moveable body runs through. And

Relative Motion, is the change of the relative place of a moving body, or considered with respect to the motion of some other body; and has its celerity estimated by the quantity of relative space run through.

As to the Continuation of Motion, or the cause why a body once in Motion comes to persevere in it: this has