514 
PHILOSOPHICAL SOCIETY OF WASHINGTON. 
used to insure verticality of the telescope, and similar observations made 
in Wisconsin, in 1887, using a mercurial horizon protected by a gauze 
cover. 
5. A comparison was also made between the results of observations 
made in the great Franco-Spanish quadrilateral of 1879, connecting the 
European geodetic system with that of Africa, and the “ Davidson ” 
quadrilateral of the U. S. Coast and Geodetic Survey in California. 
6. In both instances, u while the observing skill might be considered 
equal, superior methods and better atmospheric conditions gave some¬ 
what greater precision to the American results. 
7. In conclusion, American observers were urged to supreme exertion to 
keep pace with equally earnest brother-workers abroad, both in theory 
and practice—educating the hand to become the skilled servant of the 
head. 
Mr. Simon Newcomb then presented a communication on the 
Fundamental Concepts of Physics. 
[Abstract.] 
The subject was introduced with a twofold objection to the maxim that 
a body cannot act where it is not. In the first place, the question how 
and where a body can act can be determined only by observation, and if 
we find by observation that it does act where it is not, that settles the 
question; but, secondly and mainly, we do not know where a body is 
except by its action. When the hand comes in contact with a material 
object we infer that the object is there solely from the fact that the resist¬ 
ing force is exercised against the motion of the hand. It is commonly 
supposed that this resisting force is the effect of a repulsion exerted by 
all bodies upon others which come sufficiently near them. If we admit 
that such a repulsive force can be exerted through a space a millionth of 
a millimeter, we may with equal force conclude that it may extend 
through the celestial spaces. 
The remainder of the paper was principally devoted to the discussion 
of the probability of forming a satisfactory theory of the constitution of 
matter and of the nature of such physical agents as light, heat, and elec¬ 
tricity. The suggestion was thrown out that it might be forever impos¬ 
sible to form a rational theory of these things, owing to the fact that our 
senses afford no means of seeing what is going on in the ultimate parts of 
matter. We cannot conceive of any physical change which does not 
imply a change of something in space, but we may have to admit that 
changes may take place in the chemical qualities of bodies without any 
such change. 
