Mathematicall recreations. Or, A collection of many problemes, extracted out of the ancient and modern philosophers as secrets and experiments in arithmetick, geometry, cosmographie, horologiographie, astronomie, navigation, musick, opticks, architecture, statick, mechanicks, chemistry, water-works, fire-works, &c. Not vulgarly manifest till now. Written first in Greeke and Latin, lately compi'ld in French, by Henry Van Etten, and now in English, with the examinations and augmentations of divers modern mathematicians whereunto is added the description and use of the generall horologicall ring: and the double horizontall diall. Invented and written by William Oughtred.

EXAMINATION.

IT is certaine in the first part of this Pro∣bleme that Conicall, ••oncave and sphericall Glasses, of what matter soever, being placed to receive the beames of the Sun will excite heat, and that heat is so much the greater, by how much it is neere the point of conc••rse or inflamatio••. But that Archimedes or Proclus d••d fire or burne Shipps with such Glasses, the ancient Histories are silent, yea the selves say nothing: besides the great difficultie that doth oppose it in remotenesse, and the matter that the effect is to work upon: Now

by a common Glasse we fire things neare at hand, from which it seems very facil to such which are lesse read, to do it at a farre greater distance, and so by re••ation some de∣liver to the World by supposition that which never was done in action: this we say the rather, not to take away the most excellent and admirable effects which are in Burning-glasses, but to shew the variety of Antiquity, and truth of History: and as touching to burne at a great distance, as is said of some, it is absolutely impossible; and that the Pa∣rabolicall and Ovall Glasses were of Ar∣chimedes and ••roclus invention is much uncertaine: for besides the construction of such Glasses, they are more difficult than the obtuse concave ones are; and further, they cast not a great heat but neere at hand; for if it be cast farre off, the effect is little, and the heat weake, or otherwise such Glasses must be greatly extended to contract many beames to amasse a sufficient quantity of beames in Parabolicall and Conicall Glasses, the point of inflammation ought to concur in a point, which is very difficult to be done in a due pro∣portion. Moreover if the place be farre re∣mote, as is supposed before, such a Glasse cannot be used but at a great inclination of

the Sunne▪ by which the eff••ct of ••urning is d••min••shed, by reason of the weaknesse of the Sunne-beames.

And here may be noted in the last part of this Probleme, that by r••ason of obstacles if one plaine Glasse be not sufficient, a second Glasse may be applyed to help it: that so if by one simple reflection it cannot be done, yet by a double reflection the Sun-beames may be ••ast into the said Caverne or Mine, and though the reflected beams in this case be weak▪ yet upon a 〈◊〉〈◊〉 c••mbustible matter it will not faile to do the effect.