244; Notices respecting Neia Books. 



the intensity of heat and light that Bourne had to contend with, and 

 the then prevalent idea that heat and light (so far as the sun was 

 concerned) were necessarily in the same ratio, and essentially coin- 

 cident in their place of action, we cannot hut wonder at the opinion 

 being hazarded by a man of so sensible and modest a character : and 

 we are obliged to consider him an extraordinary person, even though 

 he mistakes (probably an error of the hand rather than the mind) 

 the side of the focus of light on which the focus of heat falls. 



V. Johannes Rohjns de Cometis. A curious specimen of the rho- 

 domontade of the astrologers of the middle ages. It appears, how- 

 ever, that Robyns had read Cicero, for part of this preface is pla- 

 giarised from him. 



VI. Two tables, one showing the time of high water at London 

 Bridge, the other the duration of moonlight. 



An extract from the first of these tables was given by Mr. Lub- 

 bock in the Phil. Trans, for 1837, p. 103, of which the editor of 

 this collection was ignorant at the time his MS. was sent to press 

 (Rara, Corrections). It is a very curious document, showing, as Mr. 

 Lubbock remarks, that the time of high water at London Bridge was 

 then " more than an hour later than at present ;" and, therefore, 

 that immense interruption to the progress of the tide in the River 

 Thames has been removed in the course of six centuries. We 

 ought not, however, to forget that great difficulties then existed 

 in determining the actual time of high water, though there can be 

 little doubt that the approximation was as correct as such circum- 

 stances would allow, and that at most the error could not be more 

 than three or four minutes. 



VII. A treatise on the Mensuration of heights and distances ifrom 

 a MS. of the I4th century. 



This treatise contains several ingenious methods of mensuration, 

 or rather of right-angled trigonometry, and is very curious as ex- 

 planatory of the practice of the times. The quadrant had then the 

 form of a square, and the unknowns were all determined by means of 

 similar triangles. Though the MS. is of the 14th century, it is too 

 full of methods adapted to different exigencies to indicate the ge- 

 neral matter of it being then of a recent date. The methods them- 

 selves are all independent of any function of the angle observed ; 

 and hence most probably this MS. is only a copy of one of a much 

 older date, and antecedent to the introduction of the Arabian tri- 

 gonometry into Europe. Being in English, it shows at least that 

 Englishmen then understood the doctrine of similar triangles. 



This " tretis" is, however, valuable on account of the very curious 

 editorial note, at pp. 56, 57, attached to the author's etymology 

 of the word " Geometri," from geos and metros. It consists in an 

 extract from a very ancient MS. in the King's library relative to the 

 time when geometry as a science was first introduced into England : 



" The clerk Euclyde on j)is wyse hit fonde 

 Thys craft of gemelry yn Ejiypte londe 

 Yn Egypte he tawghte hyt ful wyde 

 , Yn dyvers londe on every syde. 



