TOL. XVII.] yttlLOSOPHICAL TRANSACTIONS. 511 



by computation from the table, I find that there are nearly 1 5000 persons above 

 \6 and under 45, of which at least 7000 are women capable to bear children. 

 Of these, notwithstanding there are but 1238 born yearly, which is but little 

 more than a 6th part, so that about one in six of these women breed yearly ; 

 whereas, were they all married, it would not appear strange or unlikely, that 4 

 Out of 6 should bring a child every year. The political consequences hereof I 

 shall not insist on, only the strength and glory of a king being in the multitude 

 of his subjects, I shall only hint, that above all things, celibacy ought to hp 

 discouraged, as by extraordinary taxing and military service ; and those who 

 have numerous families of children should be countenanced and encouraged by 

 such laws, as the jus trium liberorum among the Romans. But especially by 

 an effectual care to provide for the subsistence of the poor, by finding them 

 employments by which they may earn their bread, without being chargeable to 

 the public. 



JVhat a complete Treatise of Navigation should contain. Drawn up in the Year 

 l685. By Sir William Petty, late F. R. S. N° I89, p. 657. 



1. What arithmetic, in whole numbers and fractions, as also in decimals and 

 logarithms, is necessary for the same ? and what books are best for teaching so 

 much of it ? 2. What common practical mechanical geometry, performable by 

 the scale and compass is sufficient ? 3. What trigonometry, right lined and 

 spherical, will suffice ? 4. How many stars are to be known ? 5. What instru- 

 ments are best for use at sea, with the construction of them, and the manner 

 of using them ? 6. The whole skill of the magnet, as to its directive virtues, 

 and all the accidents which may befal it. 7. The hydrography of the globe of 

 the earth, the views of the coast, and the description of the under water-bot- 

 tom of the sea. 8. The knowledge of winds and meteors, so far as the same 

 is attainable. Q. The history and skill of all sorts of fishings. 10. The art of 

 medicine and surgery, peculiarly for the sea. 11. The common laws of the 

 admiralty, and jurisdiction of the sea. 12. The several victuallings and 

 clothings fit for seamen. 13. The whole science of ebbing and flowing, as also 

 of currents and eddies at sea. 14. Dromometry, and the measures of a ship's 

 motion at sea. 15. The building of ships of all sorts, with the several rigging 

 and sails for each species, and the use of all the parts and motions of a ship. 

 16. Naval economy, according to several voyages and countries. 17. The art 

 of canting, rowing, and sailing, of all the several sorts of vessels. 18. The 

 gunnery, fire-works, and other armatures peculiar to sea and sea-fights. 19. 

 The art of loading and unloading the chief commodities to the best advantage. 

 20. The art of weighing sunken ships and goods, as also of diving for sunkea 



