Tycho Brake, Bacon, f4alilco, Kapler, DCS Cartes ~ w 1600 

 Thermometers invented by Drcbel ~~, ,^~ - 1610 



Napier, logarithms ,~~ ~~~ ^^, 1611 



Vernier's index made known +~~ +** *~~ 1631 



Cassini observes :i transit of Mercury *~~ *~~ 1636 



A transit of Venus first observed by Horrox ~ ,~~ 1639 



Barometers by Torricelli ~~ 1613 



Pendulum applied to clocks by Huygens 1619 



Cavalerius, Fermat, Pascal, Wallis, Hevelius 1650 



Air pump by Otto Guericke ~~~ ~~~ ~~~ *~~ 1653 



Royal Society established in London ~ ~~~ 1662 



Foundation of the Royal Observatory at Greenwich 1675 



Micrometer of Kircher ~ 1677 



Newtonian Philosophy published ~~, 1686 



Saver y had invented steam engines ~~ , 1696 



Bernoulli J., Barrow, Hooke, Leibnitz, Reaumur, 



Flasnstead, Picard, Cotes, Taylor, Halley, 1650 to 1700 



Aberration of light by Bradley ~~~ 1727 



Achromatic glasses invented , ~~~ ~~~ 1729 



Franklin, identity of lightning and electricity , 1747 



Harrison, time pieces ~ ^~^ ~~~ ~~~ 1750 



Clairaut, Maclaurin, De Moivre, Simpson, Bouguer, 



Bernouillis, Dollond, Maupertuis ~~ ~~~ ~~~ 1750 



New stile introduced into Britain ~~ *~~ 1752 



Galvanism . 1791 



Telegraph invented by the French ~~, ,,~~ 17U1 



D'Alembert, Euler, Landen, Lalande, Maskelyne, 



Waring, &c. ~-~ from 1750 to 1800 



Fora. List of the most remarkable JEras see JEra. 



CIRCLE Equations to. 



1. Let x and y be rectangular coordinates ; then if the origin be at the 

 centre, 



?/ =r V 7-3 #2- 



If atithe extremity of the diameter, 



y \/2 r jc r 2 - 



And in general if #', y be the coordinates to the centre, the equation 

 is, when the axes are rectangular, 



(.r ,r') 2 ^- (?/ ;/') 2 7-2. 

 Jlejicp every equation of l".\. (iiniejisions of the form AJ' 2 + A.?/ 2 -\> 



