6 Proceedings of the Royal Irlah Acadenuj, 



heated point, I noticed an instance of perfect rotation. Usually, how- 

 ever, the currents are formed and proceed in all directions, carrying with 

 them any grains of dust that may be in the fluid. The net- work of 

 laticiferous vessels, anastomizing with each other, lies under the in- 

 fluence of the sunlight, as an exposed plane. 



Pirst. Heat is capable of producing various currents, moving iu 

 diverse directions. 



Second. Heat is absolutely required in order that the movements 

 in the latex vessels shall be produced : under little heat they delay ; 

 more heat quickens them. 



II. — On Changes in the Physical Geography of Ieeland. By 

 Geoege Sigeeson, M. D., Ch. M., F. L. S. 



[Eead June 23, 1873.] 



It is impossible to read the first pages of our ancient annals without 

 being struck by the frequent mention of certain singular phenomena, 

 the periods of whose occurrence are referred back to the earliest com- 

 mencement of our history. With great sobriety of diction, and cir- 

 cumstantial precision of statement, we are told that in certain years 

 there burst forth certain lakes, which are duly named, and that in 

 other years there were eruptions of other lakes, and also eruptions of 

 rivers. The dates and names are set down for every case. 



Now, at first sight, these things seem so improbable, that the 

 reader is inclined to believe the record to be erroneous, either fundamen- 

 tally in fact, or superficially in the misstatement of ordinary incidents. 

 Floods, it might be argued, have been magnified into the eruption of 

 rivers, and the overfiow or inundation of a lake into the outbursting 

 of a new lake. There is another view also which is seemingly 

 shrewd and very plausible. It is that the first discovery of lakes and 

 rivers was marked down as the period of their first appearance. The 

 historian O'Halloran may be allowed to state this view, as he does it 

 with much earnestness. In reference to the recorded eruption of some 

 lakes and rivers, he says : " It is recorded that at this time there 

 were found in Ireland, but three lakes and nine rivers, whose names 

 are particularly mentioned ; but from this it appears probable that the 

 parts of the country in which these lakes and rivers appeared were 

 only what were then known ; and, that as their successors began to 

 explore and lay open other parts, the rivers and lakes then appearing, 

 were entered into the national annals as they were discovered ; but, as 

 no previous mention cou.ld have been made of them, and that the dif- 

 ferent periods at which they were found out were distinctly marked, 

 succeeding annalists have dated the first bursting forth of each from the 

 time of its discovery. Our writers are very exact in the times in 

 which these rivers and lakes appeared ; it cuts a conspicuous figure in 

 our history, and proves the extreme accuracy of our early writers ; , 



