176 GENEKAL CONDITIONS OF SCIENTIFIC RESEARCH. 



obscurity until the time comes for proving their truth. 

 The hour must come and Ute man for each new discovery. 

 Sir J. Herschel has observed : ' The greatest discoverer 

 in science can do no more than accelerate the progress of 

 discovery.' l 



That Newton's great discovery would soon have been 

 made appears probable when we consider what points of 

 knowledge had been arrived at by previous investigators. 

 The Arabian philosophers of the twelfth century considered - 

 gravity to be a force acting in a direction towards the 

 centre of the earth, and knew that it diminished with the 

 distance, but thought it decreased in a direct ratio with 

 the distance. Boulliaud, in 1645, remarked, respecting 

 the influence of gravity, that ' if attraction exist, it will 

 decrease as the square of the distance.' Borelli also, in 

 1666, maintained expressly that 'the satellites of Jupiter 

 and of Saturn move round their primary planets in the 

 same manner as the Moon does round the Earth, and that 

 they all revolve round the Sun, which is the only source of 

 any virtue, and that this virtue attaches them, and unites 

 them so that they cannot recede from their centre of 

 action.' And Hooke, in 1674, said: 'I shall hereafter 

 explain a system of the world differing in many particulars 

 from any yet known, answering in all things to the 

 common rules of mechanical motions. This depends upon 

 three suppositions: 1st. That all celestial bodies what- 

 soever have an attracting or gravitating power towards 

 their own centres, whereby they attract not only their 

 own parts, and keep them from flying from them, as we 

 may observe the Earth to do, but that they also do attract 

 all the other celestial bodies that are within the sphere of 

 their activity, and consequently that not only the Sun 

 and Moon have an influence upon the body and motion of 



1 Life of Miss Caroline Herschel, p. 248. 



