JUNE 27, 1884.] 
so often been the single purpose of so-called 
exploration ; nor is it carried out by sinking 
shafts in the centre of a mound, or cutting a 
ditch or two through it: but every foot of earth 
is removed, and the whole structure laid bare 
foot by foot. This mode of work has led to the 
discovery of singular and remarkable structures, 
not only in the mound and at the natural level 
of the surrounding land, but for six feet be- 
neath this, to the underlying gravel-deposit. 
These operations have brought so many novel 
facts to light, that we have now the right to 
class all former mound-explorations in the Ohio 
valley as so superficial as to be scientifically 
worthless, until further thorough work on groups 
not yet destroyed shall give the means of com- 
parison, and place the partial results that were 
formerly obtained in their proper relations. 
The recent explorations have shown conclu- 
sively that the mounds and earthworks in vari-. 
ous parts of the country were made at greatly 
different periods of time, and presumably by 
different peoples, even should it be ascer- 
tained that they all belonged to the great Mon- 
goloid stock, of which our Indians probably 
represent more than one subdivision. ‘This, 
however, is not yet proved ; and the conclusions 
that have been drawn from time to time, that 
there has only been one people on this conti- 
nent who made the earthworks of various kinds, 
are too hasty deductions from the present im- 
perfect knowledge of our archeology. That 
some Indian tribes made mounds and earth- 
works and fortifications is not to be questioned, 
and that others did not is probably equally true ; 
but this does not give us the right to throw over- 
board other facts tending to show that peoples 
of various stages of development, and, so far 
as craniological and artistic conclusions can be 
at present drawn, of distinct ethnical stocks, 
were also former inhabitants of this continent. 
One man will class all the past and present 
native inhabitants of all America, both north 
and south, as Indians; the next, with equal 
assurance, will state that the ancient Mexicans, 
the builders of the stone structures in Yucatan, 
the old Peruvian and other South-American na- 
SCIENCE. 7715 
tions, etc., were races distinct from the North- 
American Indians ; and there have been many 
variations from these theories. 
The fact is, we do not know who the Indians 
are, or who were the old builders of Palenque, 
of Uxmal, of Tiahuanuco, and numerous 
other old cities from Mexico to the eastern side 
of the Andes in South America. Until we 
awake to the fact that America has an inter- 
esting past, and can arouse ourselves to the 
effort of making out the ancestors and descend- 
ants of all these peoples, who have left us such 
marked differences in their architecture, their 
works of art, their customs and their languages, 
we act the part of amateurs, when from a little 
knowledge of a few of these different conditions, 
and from superficial or very general resem- 
blances, we draw hasty conclusions. Only the 
most thorough explorations, conducted by men 
who have broad views and careful methods of 
work, — men who are above being led by theo- 
ries to be maintained ; who will look at facts in 
the same manner as a geologist or a biologist 
looks at his facts, letting them lead him where 
they will, — will solve for us the great problems 
of American archeology. The days of collect- 
ors of curiosities and hasty writers are over. 
Archeology is a science, and no longer in the 
hands of the mercenary dealer and the equally 
avaricious collector of curiosities. Give the 
proper institutions the support they ask for, and 
the near future will bring valuable results. 
LETTERS TO THE EDITOR. 
x*x Correspondents are requested to be as brief as possible. 
The writer’s name is in all cases required as proof of good faith. 
Gyration of a vibrating pendulum. 
Ir a body move in any curve about any centre of 
curvature, the inertia of the body is manifested as a 
force acting in the plane of the curve, and in a direc- 
tion opposite to that of the centre of curvature; and 
if v denote the lineal velocity of the body, and p its 
distance from the centre of curvature, the force thus 
manifested will be represented by Os and is called 
the centrifugal force due the motion. 
If the body move in a straight line on a limited 
portion of the earth’s surface while the earth is ro- 
tating on its polar axis, its motion may be regarded, 
without sensible error, as being on a tangent plane; 
and because any tangent plane rotates about an axis 
