470 
7) a) 
Me wail page a eed 
P= aes {OS x ST} 
A, B, C, being the principal moments of inertia of the body, 
and J the moment of inertion with respect to the axis ON. 
The proof of Clairaut’s Theorem from the foregoing equa- 
tions formed the concluding part of Mr. Allman’s communica- 
tion. 
Rey. Samuel Haughton read a paper on a Modification of 
Mr. Green’s Formule, applicable to the representation of M. 
Jamin’s Experiments on Reflected Polarized Light. 
Dr. Petrie made the following observations upon two Irish 
inscriptions which appear, in tablets, on the sides of a stone 
which forms the upper portion of the shaft of the great stone- 
cross of Tuam, now exhibited in the Central Hall of the Great 
Industrial Exhibition ; and of which, through the kindness of 
the Fine Arts Committee, he had got casts made, to be de- 
posited in the Museum of the Academy. He remarked that 
he gladly availed himself of the opportunity now afforded him 
of making this communication, as he had, in his Essay on Irish 
Ecclesiastical Architecture, been the first to draw attention to 
this remarkable and truly magnificent remain of Irish art ; 
and more particularly as—from a recent examination of that 
portion of the monument which bears these inscriptions, and 
which portion he had not himself previously seen—he was now 
enabled to give a more complete and accurate copy of one of 
the inscriptions than that which he had already published. 
The first inscription is carved in two parallel vertical lines, 
to be read from the top downwards, and simply records the 
name of the Abbot of Tuam, successor of St. Jarlath, by or 
for whom the cross was erected. The inscription is as fol- 
lows : 
