64 ' The American Geologist. J^'^'- i^*^*- 
Tht lava in the crater showed along a line running through the 
crater northwest to southeast. There were three principal fire-fountains 
from which the lava flowed over the crater floor. Steam issued in all 
directions o^■er the whole crater floor, with an area of (three miles by 
two and one-half miles) seven and one-half miles. It is said that the 
crater floor rose 300 feet and then settled back to its old level. 
On Monday. December 7th, at 10 p. m., the last glow from the fires 
was seen and then blackness settled down over the mountain top. 
Edgar Wood. 
To C. H. Hitchcock, Hanover, N. H. 
The Dolomytes of Eastern Iowa. The experimental work in this 
investigation was done by Grace D. Bradshaw in the chemical labora- 
tory of Cornell College. The purpose was to determine whether the 
silica exists in a' iree condition, or is in the form of a silicate ; also to 
ascertain whether the iron is in the ferrous condition as carbonate, or 
is in the form of ferric oxide. The rocks abound in many parts of low-i 
and belong to the Niagara formation. The stratified character, even in 
a small field section, is apparent, and the layers differ somewhat in 
composition as shown by the varying amounts of iron visible in differ- 
ent portions. The rocks are used as building stone to manufacture 
quick-lime, and in McAdam paving. 
To answer the first question as to the condition of the silica six pairs 
of determinations were made as follows : 
(a). A gram of the finely powdered rock was placed in a small 
beaker, and covered with a watch glass, a small quantity of dilute hy- 
drochloric acid was added and the carbonates were dissolved by careful- 
ly heating to the boiling point. The insoluble portion, which is the sili- 
ca, was filtered off, dried in an air bath, and the weight determined. 
(b). A gram of the fine powder placed in a porcelain evaporating 
dish of loocc. capacity was treated with dilute hydrochloric acid, and 
covered with a watch glass. It was warmed on the water bath until 
there was no further evolution of carbon dioxide. The watch glass 
was removed' and the dish was kept on the water bath until crystals 
began to appear. Then as the drying continued, the substanc? was con- 
stantly stirred with a glass rod until a fitae dry powder resulted. The 
powder was then moistened with a few drops of concentrated Iwdro- 
chloric acid, and 20cc. dilute hydrochloric acid (equal parts of concen- 
trated hydrochloric acid and water) and about the same quantity of 
water were added. The contents of the dish were then filtered and the 
The results for the two methods were as follows : 
silica determined. 
(a). 
I). 
0.78 i 
2). 
0.76 " 
.3). 
0.81 " 
4). 
0.87 " 
.0. 
0.94 " 
6). 
0.94 " 
(b). 
I) 
0.75 
2) 
0.90 
3) 
0.85 
4) 
0.91 
5) 
0.87 
6) 
0.73 
