May 24, 1858.] PHYSICAL GEOGRAPHY— CHANGES OF THE SURFACE. 325 
PHYSICAL GEOGRAPHY. 
Changes of the Surface of the Globe. — Having gone through a variety 
of details respecting the progress of our science in the four quarters of 
the globe, I may now draw towards the end of this Address by a 
few notes on the general and important subject of Physical Geo- 
graphy. 
M. de Francq has recently occupied himself with some laborious 
researches respecting the laws which may be recognized in the 
distribution of land and sea, and of surfaces of relative elevation 
and depression on the general outline of the globe. Assuming the 
whole mass of the earth to have been primitively in a state of 
fusion, and an outer crust to have been formed by cooling and con- 
sequent solidification, he concludes that when this process had 
arrived at a certain stage, the shrinkage of the interior nucleus from 
continual loss of heat would be greater than that of the outer crust 
from the same cause, and that consequently the solid superincum- 
bent crust would partly lose its support beneath, and be left in the 
position of an arch or dome too weak to support itself. The result, 
it is supposed, would be that the shell would collapse by its own 
weight, and that its surface would be elevated into ridges and 
depressed into furrows in various directions, producing the inequal- 
ities which we now witness. In this idea there is nothing new ; 
but M. de Francq has another assumed principle which forms the 
base of his very laborious researches. He assumes that, the effect of 
this partial crushing of the earth's solid crust will manifest itself equally 
along every great circle of the globe — a result which he pointed out to 
myself on a small hollow globe of thin flexible substance when 
affected by the tightening of strings which draw it into depressions 
which are accompanied by parallel depressions. It might perhaps 
be supposed that this effect on proposed great arc would be 
brought out, the literature of researches in Abyssinia has received in the past year a 
copious and instructive addition by the publication at Rome, through the Propaganda 
Congregation, of the work entitled ‘ Yiaggip e Missione Cattolica fra i Mensa, i Bogos e 
gli Habab,’ by the missionary Giuseppe Sapeto. First visiting Abyssinia in company 
.with the brothers d’Abbadie in 1838, and quitting it from bad health after a sojourn of 
five years, Sapeto made his last journey from Massowah in 1851. His personal adven- 
tures, which are told with great animation, form a part only of the contents of this well- 
filled volume, in which the author has amassed much valuable information respecting the 
physical geography, ancient divisions, and general history of this country, so gifted by 
nature, and now in so fallen a state, accompanied by striking sketches of its animal and 
vegetable productions. Me has further added annotations from national documents in the 
Ethiopian language, with translations into Italian. I am indebted to my friend Dean 
Milman for an acquaintance with this work, which I had not seen when the Address was 
delivered, and which is well worthy of perusal by geographers and scholars . — June 30, 1858. 
