is in,&rtJcrto ehuidatetnore clearly th 

 pf Kjepler s Laws]. 



Fig.l. 



The CentivFiffure represents tlieAnraial 



Rjevolutionofthc Earth roundtheSi 



on its Orbit, which is an Ellipse , th 



eccentricity of which is about 583,691 



leagues, and onthe first o feachMonih. 



The graduated Circle which at.asmaR 



distance surrounds the North Polein 



each figure of the Earth .shews the 



Parallel of GreatBrituin, this Circle 

 ; is divided into 24 hours . 



The limu -e to the rightmarks the hour 



of Sun-rise, that to the left the hour 



of Sun-set. Thepoint o indicates 



the position of Great Britain/with 



reference, to the Sun at the various 



hours of the Day andNight- for 



Example, it is 2 O ' Clock A.%Lonthe 



first of June, and the horary Circle 



shwsusthatatthistimethehourof^^ 



Sun-rise is 4 * 3 andfhatofSunrsct ^L, 



7 h 51 theNight therefore will conti- 



-nue 2*^ 3 longer. Again onthe first 

 \ of December the Sunrrises at 7^40 

 | and Sets as the horary Circle indicates 

 | at 4^4 the time supposed being 1 

 I 1n day will continue 2^ 24 long i 



At this period o fthe Tear the Earth approaches 



the Winter Solstice whenits North Pole is en 



-veloped in darkness for two Months will have 



reached the middle of its long Night 



Fig. 2. 



Suppose amoving bodySL subjected to the influence 

 of two forces. One in the direction Hi, S . the other in the 



I direction ~HL X, the intensify being indicated by the right 

 lines HL, P. and HUV the moving body can neither go towards 

 S nor JO, but must take an intermediate Course 1IL, O , with a 

 Velocity represented by HL,-**. It is thus clear that the moving ^ 

 body~B\* will take the same direction and have the same Velocity 

 as One force represented in3fagnitude by HL -*-* andin direction by 

 DL O, would hai'e imparted to it. The name Residtant or eauu'alent force 

 is gib' en to this . Whena Curve is described by Virtue of a force directed tc 

 a fixed point S, it may beresoh'edintotwo-Oneinthe direction of the Radius 

 H^-S, the other of the Curve^ A . This accelerating force is supposedto act only attlie 

 beginning of eaehnwmeritwhile the Motionis uniform the VectorEadius Ilji S.thenwill 

 trace a small triangle 1 ^ S A . If this force ceased to act the following moments the VectorKadius 

 wouldtracc afresh triangle cqualto thefirst. But,atthe beginning of the nejctmomeritthe accelerating 

 force ~H\jL k. combines withT^Q.and causes the moving body to exhibit the effects of the resultant force A 1H, . 



j the sides of which A p, A B represent these forces . 



\ : , . 



