C 3 21 H 
XVII. Observations on the Measurement of three Degrees of the 
Meridian conducted in England by Lieut. Co/. William Mudge. 
By Don Joseph Rodriguez. Communicated by Joseph de 
Mendoza Rios, Esq. F. R. S. 
Read June 4, 1812. 
The determination of the figure and magnitude of the earth 
has at all times excited the curiosity of mankind, and the his- 
tory of the several attempts made by astronomers to solve 
this problem might be traced to the most remote antiquity. 
But the details of the methods pursued by the ancients on this 
subject being extremely vague, and their results expressed in 
measures of which we do not know the relation to our own, 
in fact give us very little assistance in learning either the 
figure or dimensions of our globe. 
It was not till the revival of science in Europe that the 
two great philosophers, Huyghens and Newton, first en- 
gaged in the consideration of this question, and reduced to 
the known laws of mechanics, the principles on which the 
figure of the earth should be determined. 
They demonstrated that the rotatory motion should occa- 
sion differences in the force of gravity in different latitudes, 
and consequently that parts of the earth in the neghbourhood 
of the equator should be more elevated than those near the 
poles. 
The most simple hypothesis, which first presented itself to 
