Notices respecting New Booh. 24<3 



nomine Algus, unde algorismus nuncupatur, vel ars numerandi, vel 

 introductio in numerum." And it is remarkable that the same state- 

 ment is supported by other authorities. Johan. de Norf. adds, 

 *' Rex quondam Castellise." However, the tract being now before 

 the public, we need say no more concerning it, as every one inter- 

 ested in the subject can consult it at his leisure. 



II. A method used in England in the fifteenth century for taking 

 the altitude of a steeple or inaccessible object. 



This is a tentative method adapted to the observer being de- 

 stitute of the necessary surveying instruments. English mathema- 

 ticians were then, as the editor observes, " skilful in the application 

 of the quadrant, and all other known scientific instruments." "We 

 rather think it a contrivance such as we have said than the device 

 of the more ignorant classes. Perhaps it may partake of both. 



III. A treatise on the numeration of Algorism : from a single leaf 

 of vellum found loose in an old MS. on astronomy, in the editor's 

 possession. It is a treatise on what we properly call "numera- 

 tion," or the local value of the digits composing a number. It is 

 intended, evidently, as the introduction to a treatise on arithmetic 

 in English, and probably formed part of one. 



IV. A treatise on the properties and qualities of glasses for optical 

 purposes, according to the making, polishing and grinding of them : 

 by William Bourne. 



Bourne is well known to readers of works of the sixteenth cen- 

 tury. He was a skilful navigator, and possessed a very inventive mind* 

 Some, but a very incomplete account of him, may be seen in Dr. 

 Hutton's Mathematical Dictionary. 



This tract it appears was drawn up at the request of " Elizabeth's 

 great minister," and is inscribed to him ; and Burleigh's object 

 seems to have been to ascertain something relative to the art of 

 seeing hidden things by means of glasses, — a favourite belief of that 

 time, arising probably from the pretensions of Dee and Digges to 

 the possession of such power. Bourne gives a plain and succinct 

 account of the properties of reflecting and refracting mirrors, in the 

 main, derived evidently from experiment. With one or two excep- 

 tions, the descriptions are correct. His lens of a foot diameter, how- 

 ever, is merely a conjecture of what may be possible, and evidently 

 had never been made or seen by him. 



He does not give the slightest hint of combining two refracting 

 mirrors, so as to form a telescope. This was reserved for Galileo. 

 Still he proposes the employment of a concave reflector to increase 

 the magnitude of the image given by a convex refracting lens. A 

 reversal of this process would have led to the most important re- 

 sults, and might have long anticipated the suggestion of Mersenne 

 and the invention of Gregory. 



There is one point exceedingly curious in this treatise. He states 

 the foci of heat and light are not identical ; a circumstance which 

 we believe had never been suspected by philosophers till Sir William 

 Herschel established it in the Philosophical Transactions for 1800. 



When we consider the want of any accurate means of estimating 



R2 



