628 
CURRENT NOTES ON PHYSIOGRAPHY. 
THE ILLINOIS GLACIAL LOBE. 
THE elaborate monograph by Leverett on 
‘The Illinois Glacial Lobe’(Monogr. XXXVIIL., 
U. S. Geol. Surv., 1899, xxi + 817 p., 18 maps, 
6 pl. 9 figs.) has, apart from its high worth as 
the most detailed study of its kind yet published, 
a great vaiue to the physiographer in warrant- 
ing a generic treatment of the class of forms 
that it describes. It is not merely that one may 
find, in this or that part of Illinois, till plains, 
moraines, loess beds, gravel trains and the like, 
but that these several parts have a form and 
distribution characteristic of their class. Since 
Chamberlin’s recognition of the lobate margin 
of the glacial sheet indicated by the peculiar 
arrangement of its terminal moraines, evidence 
in great variety and quantity has been discov- 
ered to confirm his generalization ; and we have 
now come to possess good ground for regarding 
the moraines and the associated deposits and 
erosion forms of lobate ice sheets as characteris- 
tic elements of our topography, on a large scale 
horizontally, although of small vertical relief. 
The type form is relatively simple ; it consists 
of many parts, but they are systematically and 
genetically related in a highly specialized unit ; 
a unit whose empirical description is as baffling 
as would be the mention of an oak tree in terms 
of its items in arbitrary order instead of by its 
generic or specific name, but whose explanatory 
description is as easily apprehended as is that 
of a mature river-and-valley system. The as- 
sociation of several units by repetition of proc- 
ess provides something of the variety of nature ; 
special features due to local condi.ions require . 
an elastic instead of a rigid conception of the 
type; and the detection of the changes suffered 
by the initial forms with the passage of time 
affords a pleasing exercise for observation and 
understanding. An abstract of the facts thus 
understood, with Illinois as the field of their 
typical occurrence, should enter the high schools 
of this generation. Room may possibly be pro- 
vided for them (by the exclusion of less worthy 
matter) in the grammar schools of the next 
generation. A closer study of the facts affords 
good exercise for collegiate students who have 
previously learned an outline of them in school. 
The details yet to be discovered in the field 
SCIENCE. 
(N.S. Vou. XIII. No. 329. 
will tax the patience and ingenuity of the inves- 
tigator for years tocome. The monograph is a 
worthy monument to the skill of the observer 
who executed it, to the insight of the leader 
who planned it, and to the broad policy of the 
organization that supported its preparation and 
publication. 
THE ALBAN MOUNTAINS. 
THE group of extinct voleanoes southeast of 
Rome, sometimes known as the Alban moun- 
tains among English writers, but called Vuleano 
Laziale by the Italians, is elaborately described 
by Sabatini (Mem. descr. Carta geol. ital. X, 
I Vulcani del |’Italia centrale e i loro prodotti. 
ParteI., Vulcano Laziale. Roma, 1900, pp. xv 
+ 392, 9 pl., 2 maps). The mountain group is 
the complex product of successive constructive 
and destructive actions. A large volcano of 
about 20 kil. diameter lost its upper portion 
and then remained as a horseshoe mountain 
(caldera) now somewhat dissected and open to 
the southwest. Its central floor had an alti- 
tude of 400 or 500 met., and its rim, of 600 to 
800 met. This structure is called Cratere 
Tuscolano. A second voleano, called Monte 
Albano or Laziale, was built on the same axis 
as the first ; its basal diameter being 4.5 or 5 
kil., and its altitude 956 met. It has a crater 
200 met. deep, open to the northwest. At a 
still later time, three more or less complex 
basins or calderas were formed on the south 
and southwest of the central axis; they now 
contain lakes Nemi and Albano, of which some 
admirable views are given, and the plain of 
Ariccia. Lavas seem to constitute only asmall 
portion of the volcanic mass. Its chief con 
stituent is tufa, which Sabatini explains as suc- 
cessive deposits of volcanic ashes washed by 
rains, disregarding their suggested origin in 
torrents of mud ejected from the craters. En- 
gulfment is not accepted as a satisfactory 
explanation either of the great Cratere Tusco- 
lano or of the lake basins, but the argument 
for the exclusion of this process does not seem 
demonstrative. The volume of ejected ma- 
terials is estimated to be about 200 cubic kilo- 
meters. More than half of the memoir is given 
to local and petrographic details. A bibli- 
ography occupies 22 pages. The colored geo- 
