APPENDIX. 303 



naturalist, pre-occupied with old ideas, and wishing as he 

 himself said, to respect the reputation of a fellow- 

 labourer, whose previous works he esteemed, did not 

 think it necessary immediately to communicate the 

 result to the Academy. He did, however, make it 

 known in 1727, but without himself adopting it. Pey- 

 sonnel's discovery was contested until the experiments 

 made by Trembley *, on the fresh-water hydra had exhi- 

 bited in the latter a naked type of the Coral Animal and 

 other Zoophytes. All doubts were at length finally re- 

 moved by the works of two members of the Academy, 

 Guettard f and Bernard de Jussieu, who, in 1741, visited 

 the sea coast with the view of verifying Peysonnel's 

 observations. 



NOTE VI. 



Kepler, who was born in Wurtemburg in 1571, 

 and died at Ratisbon in 1630, was to a certain extent 

 the precursor of Newton. He was one of the first 

 who applied mathematics to physics ; he completed the 

 RudolpTiine Tables, which had been begun by Tycho 

 Brahe J, reformed the Calendar, and published several 



* Trembley, who was born at Geneva in 1700, and died in 1784, 

 has immortalised his name by the discovery of the fresh-water 

 hydras, and by the curious and exact experiments which he made 

 on these animals. 



t Guettard, a distinguished physician and mineralogist, was born 

 at Etampes in 1715, and died at Paris in 1786. 



{ Tycho Brahe, who was born in 1546, and died in 1601, 

 remains celebrated in the history of astronomy for his love of that 

 science and for the invention of a system which may be regarded 

 as intermediate between those of Ptolemy and Copernicus. Accord- 

 ing to him, the earth occupies the centre of our system, but the sun 

 in turning round the earth is accompanied by the superior planets, 

 which serve it in the capacity of satellites. This system, which 

 appeared to reconcile the progress achieved by modern science with 



