304 PHILOSOPHICAL TRANSACTIONS. [aNNO 1747- 



to have been altered by him in a very remarkable manner from all the former 

 printed editions. And though he acquaints us he had met with some variation 

 in the manuscripts, yet he appeals to none ; nay, he even says expressly, that his 

 amendment was purely made on conjecture; whence we may safely conclude, 

 that it stands unsupported by any various reading or authority whatever. He 

 also acknowledges that all the printed editions conspire in another reading, which 

 Mr. F. has found to be true in several he has had occasion to look into, with 

 this only variation, that whereas the first edition in 1469, and several of the fol- 

 lowing ones, print the word quinta at length, and xxx only in figures; some of 

 the latter ones, and that by the Elzevirs particularly in l633, print both the 

 words at length. And the plain meaning of the passage is only this, that the 

 length of the shadow of a gnomon, or upright style, at noon, on the day of the 

 equinox, is in Egjpt little more than half the height of the gnomon; that the 

 same at Rome wants a Qth part of that height; that at Ancona the height of the 

 gnomon exceeds the length of its shadow by a 35th part, or is in proportion to it 

 as 35 is to 34; and that in the part of Italy called Venetia, the length of the 

 shadow, and the height of the gnomon, are equal to each other. 



The particulars here mentioned are respectively true, in the 4 following lati- 

 tudes, 26° 34', 41° 38', 44° 10', and 45°. The first of which is the latitude 

 of the middle parts of Egypt, and the last that of several places in the territories 

 of Venice, the city itself standing, according to Manfredi's table, in the latitude 

 of 45" 33', and Padua in that of 45° 28'. 



It therefore appears on the whole, that this text needed no correction ; and 

 for the observation, that 35 parts were too many for a gnomon to be divided 

 into, it will be found to have very little weight, when it is considered, that the 

 ancients made use of very large gnomons on these occasions; that one of the 

 obelisks now standing at Rome, that of St. John's Lateran, is in height 108 

 English feet, without the pedestal ; and that the other, still buried under the 

 Campo Marzo, which was formerly used for this very purpose, wanted but little 

 of the same height. The 35 th part therefore of the height of such a stone, 

 did not fall short of 3 English feet; a much less quantity than which would 

 easily discover itself in the shadow, whose length, notwithstanding all difficulties 

 arising from the penumbra, might certainly be determined to less than half 

 a foot. 



It may be just added to this remark, from the description given by Pliny of 

 this gnomon, lib. 36, § xiv, of the obelisks, that there was laid down, from the 

 foot of the obelisk northward, a level pavement of stone, equal in breadth to the 

 breadth of the obelisk itself, and equal in length to its shadow at noon on the 

 shortest day; viz. that its length was to the height of the obelisk nearly as 22 

 to 10; and that into this pavement there were properly let in parallel rulers of 



