75 



and, however we may simplify it, the calculations are likely 

 to be very troublesome. Even the supposition of a resist- 

 ance proportional to the square of the velocity (which is 

 usually considered as an approximation in questions of this 

 sort), would lead to complicated results. It may be ob- 

 served, that the motion of the k'llee is rudely imitated in 

 the familiar experiment with a card, cut into the form of 

 a crescent, and sent off by a fiUip, so as to spin in its own 

 plane. 



Mr. Petrie read the concluding portion of his paper " On 

 the Antiquities of Tara Hill." 



In this, as well as in the preceding part, the author has 

 endeavoured to ascertain from historic evidences, not only 

 the period to which each of the monuments now remaining 

 should be referred, but also the date of those of which no 

 vestiges exist, but whose features and locahties are described, 

 in ancient documents. In this investigation, the author 

 brought forward a great number of ancient Irish authorities 

 not hitherto used or translated, of which one of the most 

 curious and interesting is a description of the banqueting 

 hall or house of assembly, written by Cinaeth O'Hartigan, 

 a celebrated poet of the tenth century. From all these docu- 

 ments it appears, that, with the exception of the original 

 Tuatha Dedanann cahir, and coronation stone, all the monu- 

 ments now or formerly existing on Tara Hill may be classed 

 under two distinct eras, both within the limit of authentic Irish 

 history. The first and less important class comprises the monu- 

 ments belonging to the age of the hero CuchuUin, who died in 

 the early part of the first century ; and of these there are no 

 remains. The second — to which nearly all the existing monu- 

 ments belong — extends to the time of the monarch Cormac 

 Mac Art, in the third century. There are only two or three 

 monuments of later date. From these facts, the author con- 

 cludes, that, before the latter period, Tara had attained to 



