400 



raent, as well as the branched and taper roots of those soM'n in a soil 

 superficially rich, admit of a similar explanation. So also when the 

 seeds of the bean were placed to vegetate beneath the mould of an 

 inverted pot, the lower surface of the radicles, being exposed to dry 

 air, were rendered rigid and incapable of emitting fibrous roots; while 

 their upper surface in contact with the mould, being preserved in a 

 due state of moisture, emitted fibres in that direction alone in which 

 proper food was to be procured. 



In confirmation of this explanation, the author made a correspond- 

 ing experiment, in which water was so constantly and abundantly 

 supplied, that every part of the radicles was kept equally wet, and 

 then they emitted fibres perfectly obedient to gravitation, without 

 being influenced by the soil above them. 



The strength of roots, by which they appear to be wisely adapted 

 to their situations of exposure to the violence of winds, is traced by 

 the author to the operation of another cause, noticed in a former 

 memoir ; for the immediate consequence of motion upon the roots, 

 as well as upon the branches, is a deposition of alburnous matter 

 upon the part moved ; and hence those roots which immediately join 

 the trunk of an insulated tree become strong and rigid, but diminish 

 rapidly in bulk as they recede from the stem and descend into the 

 ground. But in a sheltered valley, on the contrary, where a tree is 

 protected by its neighbours, and little agitated by winds, the roots 

 grow long, and continue slender like the stem and branches, and 

 hence comparatively much less of alburnous matter is expended be- 

 neath the ground. 



In the whole of this arrangement the author sees much reason to 

 admire the simplicity of the means employed by the wisdom of na- 

 ture, but is unable to trace the existence of anything like sensation 

 or intellect in the plants themselves. 



On the Solar Eclipse which is said to have been predicted by Thales. 

 By Francis Baily, Esq. Communicated by Humphry Davy, Esq. 

 Sec. R.S. Read March 14, 1811. [Phil. Trans. lSll,p. 220.] 



Notwithstanding there may be few facts in ancient history which 

 have given rise to more discussion, this subject still appears to the 

 author to admit of elucidation ; for though chronologists have availed 

 themselves of the aid which astronomy could give them in fixing the 

 exact time when this event occurred, and thereby ascertaining the 

 dates of several other events, yet among the various periods assigned 

 for this eclipse by different authors, we find a difference of no less 

 than 43 years between that assigned by Scaliger, who supposed it to 

 have happened on the 1st of October, 583 B. C. ; and that supposed 

 by Volney, in his Chronologic d'Herodote, who fixes it on February 3, 

 626 B. C. The results to which most confidence has been hitherto 

 attached, is, in fact, very nearly the mean between these extremes, 

 and is that preferred by Bayer, in his Chronologia Scythica, published 

 in the Petersburgh Memoirs for 1728. 



