; 
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75 
and, however we may simplify it, the calculations are likely 
to be very troublesome. Even the suppositicn 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 kilee is rudely imitated in 
the familiar experiment with a card, cut into the form of 
a crescent, and sent off by a fillip, 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 localities 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 Cuchullin, 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 
