PRESIDENT'S ADDRESS. 7 



covering the traces of the fearful bombardment which had 

 torn its surface and made it in the winter a dreary waste of 

 mud and water. By regularly screening plants of Tropaeolum 

 during certain different intervals of the day considerable 

 variations have been induced in colour and scent and even in 

 structure, extra petals and spurs being formed under certain 

 treatment. 



GEOLOGY. 



The geological age of the earth, that is, as I understand 

 it, the space of time since the first rocks were formed by 

 denudation, has been calculated in various w r ays which do 

 not all agree. Thus from measuring the rates of denudation 

 now going on, the age of from 100 to 150 millions of years 

 has been deduced. Astronomy gives rather less. Calcula- 

 tions based on heat have been entirely upset by the discovery 

 of the heat -producing properties of radium and radio-active 

 elements, which exist all over the earth's surface. In con- 

 nection with this discovery the age has, however, again been 

 calculated on the basis of the time required for radium to pass 

 through its transformations and the ratio of the quantity 

 of lead to the quantity of uranium. This gives a much greater 

 time, amounting to 1,500 millions of years ; but by more 

 recent investigations of the amount of lead in Ceylon thorite, 

 the age of 140 millions has been found, wnich is fairly in 

 agreement with some other deductions. There are, however, 

 some reasons for supposing that the decay of uranium may 

 have been more rapid in early times, whicn would bring down 

 the result of 1,500 millions to a figure more nearly approach- 

 ing the other conclusions. It has been thought that the 

 apparent greater fiequency of earthquakes at night than in 

 the daytime was owing to their being more easily peiceived 

 during the quieter hours ; but on counting the more intense 

 Italian earthquakes only and omitting the smaller ones it 

 was found that no less than 865 occurred at night to 638 

 by day, which strongly supports the belief in question. A 

 bad earthquake occurred in New Zealand last August, doing 



