542 PHILOSOPHICAL TRANSACTIONS. [aNNO 1721. 



and dividing it into small pieces, he examined them by the microscope, when 

 he saw very clearly the pores through which the perspiration or exhalation is 

 performed. He also perceived several small hiatuses which transmitted the 

 light. These were seen more distinctly when the pieces of the leaf were become 

 somewhat dry. On examining the leaves of another box-shrub, both in the 

 fresh and dried state, he saw the pores or spiracula more distinctly than he had 

 seen them in any kinds of fruits. Having measured one of these leaves, he 

 found its length equal to -fV oi an inch, and its breadth to -^ of an inch. 

 Now, let it be supposed that the figure of such a leaf is oval, then the length 

 and the breadth being added together, the number will be J 3, the half of 

 which will be 64-. But let it be supposed that the same leaf, after adding toge- 

 ther the length and the breadth, is circular; and that its diameter is equal to 

 6-i^-tenths of an inch. 



Now, on placing by the side of the aforesaid leaf a hog's bristle, and viewing 

 both together through the microscope, it appeared that 12 pores of the box- 

 leaf, if they lay close together, were equal in length to the diameter of the 

 hog's bristle. But 60 bristles were found equal to an inch; whence it follows, 

 that every 10th part of an inch is equal to 6 diameters of a hog's bristle; and 

 that the half diameter of a box-leaf is equal to IQi diameters of the said bristles; 

 which 194- diameters being multiplied by 12, that is by the number of pores, 

 will give 234 as the half length of the diameter of a box leaf. 



Now to calculate the contents of such a circle it must first be observed, 

 that the proportion between the square of the diameter of each circle and the 

 contents of the circle itself, is as 14 to 11. Hence it follows, that on one 

 surface of a box-leaf there are 17209O pores; but as there is an equal number 

 on the other surface, the collective number of pores (to a single leaf) by means 

 of which perspiration and exhalation are carried on, amounts to 344180. 



In the concluding part of this communication Mr. L. observes, that the 

 downy hairs on peaches appear to be equal in number to the pores seen on 

 [other] fruit. The down upon a quince is not less than that upon a peach. 



Remarks on some Attempts made towards a Perpetual Motion, By the Rev. Dr. 

 Desaguliers, F. R. S. N° 369, p. 234. 



The wheel at Hesse Cassel, made by Orfireus, and by him called a perpetual 

 motion, has of late been so much spoken of, on account of its phaenomena, 

 that many people have believed it to be actually a self-moving engine : and 

 accordingly have attempted to imitate it as such. Now as a great deal of time 

 and money is spent in those endeavours, I was willing, for the sake of those 



