Geysers of the Yellowstone River, Wyoming Territory. 105 
mode of formation of pearls and the rounded masses which, united 
together, constitute the dentine of teeth, and which in that substance 
are often so loosely adherent one to the other as to leave cavities 
known as “ interglobular spaces,” and the existence of which is by 
some observers denied, the appearance of them in tooth sections 
being considered “ optical illusions.” I now exhibit one of these 
silicious balls thus sectionized or cut down to a thin slice which 
runs directly through the centre of the mass, and viewing it by 
means of a pocket-lens will show plainly how it has been formed. 
At first, the silicious matter has been deposited from solution upon 
the sides of the geyser in the vegetation, like masses shown. 
Although they seem pretty strong, yet they are liable, on account 
of their porous nature, to be broken so that at some time a small 
mass has been broken off and rolled and tossed about in the basin 
until it has gradually come to be covered over with a smooth coating 
of the same material. Thereafter it has rested for awhile some- 
where within the basin, so that it has been again encrusted with 
rough material, and dropping down into the tube of the geyser, has 
again been thrown about until a smooth coat has formed over the 
rough one, and so on alternately rough and smooth coats have been 
deposited. It will be seen that the specimen I exhibit has several 
of these alternate compact and porous coatings, so that to the naked 
eye it almost seems to have an organic structure. 
These specimens were brought home by the exploring party 
under the command of Dr. F. Y. Hayden, United States’ geologist, 
who has for some time been engaged in the examination of the 
Yellowstone Park, in Wyoming Territory, under the direction of 
the Department of the Interior ; the survey being known as the 
United States’ survey of the Territories. Dr. Hayden has brought 
home many specimens of the Diatomaceae from the geysers, as well 
as several earths containing the silicious remains of those organisms, 
and these he has put into my hands for examination and report. 
Further collections will be made, and the results of the examina- 
tions published hereafter. In the meantime, Dr. Hayden has 
kindly consented to my making known here and elsewhere the 
results of my examinations, which I shall do from time to time. 
— Read before the Lyceum of Natural History, Neiv York, 
March 25, 1872. Sent to ‘ M. M. J.’ by the author. 
