322 llie Avierican Geologist. November, 1897 
Rohn's Collection of Lake Superior Rocks. 
It is a pleasure to commend to geologists the collections of 
rock specimens illustrating the petrography of the lake Su- 
perior region, which have been prepared by Mr. Oscar Rohn 
of Madison. Wisconsin. 
The collections are of a high order of excellence. The spec- 
imens are of the freshest material from localities selected un- 
der the supervision of professor Van Hise and are of remark- 
&\)\y uniform and correct proportions. 
They are accompanied by large chips for the preparation 
of thin sections. They illustrate the pre-Cambrian formations 
of a classical region and are rendered increasingly valuable 
by the references which accompany each specimen to the works 
of Pumpelly, Marvine, Irving, Van Hise, Lawson and Bayley. 
It is possible, with such a collection, to master the petrog- 
raphy of this famous district to a degree which would be oth- 
erwise unattainable. 
The remoteness of the region and the expense of a journey 
render a visit impracticable to the average student. 
Such typical illustrative material, systematically described 
by high authorities, assists in the understanding of all meta- 
morphosed crystalline rocks and is invaluable to educationai 
institutions and to students of pre-Cambrian geologj^ in any 
country. f. b. 
The Terminations -ic ani> -ical. 
There is much confusion in the use of these affixes, and the 
following rule, promulgated by the U. S. Geological Survey, is 
not only authoritative and well founded, but has been very 
generally adopted by the geologists of the United States. 
N. H. W. 
27. To insure uniformity of practice in the spelling of a large class of 
scientific words ending in ic and ical, as geologic, geological, geographic,, 
geographical, etc., the following preferences are suggested for the con- 
sideration of those who demur to the practice of dropping the al entire- 
ly — the only usage deemed ctjnsistent with the claims of an improved 
orthography : 
(a) Terms designating natural phenomena, relations, conditions, pn> 
ducts, etc., may end with ic. 
(b) Terms designating the works of man — research, literature, spec- 
ulation, etc.,— may end with ical. 
Applying these rules to the terms geologic and geological for example, 
we get : 
