62 Trof. F. IF. Hutton — On Geological Nojnenclature. 



The regional systems and series would, of course, have geographical 

 names, but the names of the chronological divisions should not be 

 geographical, as they would be made for palEeontological reasons. 

 We have very good chronological names for the four great eras, and 

 the names of the Cainozoic periods are well adapted for introduction 

 into the chronological scale as divisions. What is wanted are new 

 names for the divisions of the Mesozoic and Palseozoic eras. The 

 Archaean need not be divided until some means of correlating the 

 systems has been discovered. These divisions would form a com- 

 plete sequence, and it would be as impossible to intercalate a new 

 division as it would be to put in a new era between the Palgeozoic 

 and Mesozoic. But as our knowledge of palaeontology advanced, it 

 might be found advisable to make subdivisions in some cases, and 

 for this reason the names of the divisions should not be Upper, 

 Middle, and Lower. 



One word more as to what I understand by systems. These would 

 be separated by well-marked unconformities — physical or paleeonto^ 

 logical — over the whole or the greater part of the I'egion, and would 

 show important geological changes in the region. Consequently they 

 would have very unequal chronological values. In one region there 

 might be only one Cainozoic system, while in another region it might 

 be necessary to establish three or four systems. The}' would there- 

 fore bear no relation to the chronological divisions, which themselves 

 would represent, as they do now, very unequal portions of time. 

 The duration of the divisions would depend on the rate of biological 

 change. The duration of the systems would depend on the frequency 

 of important changes in the physical geography of each geological 

 region. Mr. Blanford says that " the principal divisions should be 

 as nearly as possible of equal value," ^ and no doubt this is theoretically 

 true as regards the chronological divisions, but it would be difficult 

 to carry out in practice, as our geological chronometer — biological 

 change — has been going faster and faster. 



Of course I do not pretend that there is anything new in these 

 remarks. Geologists are applying the principle in all parts of the 

 world. Even in England, as soon as Archasan rocks were discovered, 

 new names were given to them, because it was seen to be impossible 

 to correlate them with the previously-established Archaean systems 

 in Canada. All that I advocate is that the principle should be carried 

 out methodically by putting the European rock-systems on the same 

 footing as the rock-systems of other parts of the world, and by 

 drawing up a chronological scale to which all systems might be 

 referred. 



Canterbury College, Christchurch, 

 New Zealand. 



' Geological Magazine, July, 1884, p. 319. 



