267 
GREENWICH OBSERVATORY. 
By JAMES CARPENTER, F.RA.S. 
T HERE are few scientific institutions whose objects are so 
little understood, and whose labours are therefore so likely 
to be misjudged, as an astronomical observatory of the character 
of the national one at Greenwich. Even those who possess 
some knowledge of astronomy, who read its literature, and take 
a warm interest in its salient achievements, are frequently little 
or not at all conversant with those departments of the science 
that are perforce pursued in an essentially practical establish- 
ment, where the sun may be observed day by day without a 
moment’s thought being given to his spots, the moon watched 
by night without a care for her physiography, and where the 
planets and stars are subjects of a system of close observation 
which, however, gives no heed to questions concerning their 
physical nature. 
It happens, from a circumstance that will bye-and-bye appear, 
that the present is an opportune time for reviewing the history 
of the Observatory at Greenwich and its relation to current 
astronomical science ; but it may be mentioned that the 
appearance of this article at this opportune time is merely 
accidental. 
To start with a just idea of the very definite aims of the 
Observatory, we should clearly recognise the circumstances that 
led to its foundation. It was born of a necessity that arose 
from that extension of British navigation which was, at least 
partially, a consequence of the passing of the Navigation Act of 
Charles II. The necessity was a means of obtaining the longi- 
tude at sea. The latitude, we may remark, presented no 
difficulty whatever. A method for longitude had for more than 
a century existed in theory ; for Apian in 1524, Gemma Frisius 
a few years later, and Kepler subsequently, had proposed the use 
of lunar distances in the very form that now universally obtains. 
The method may be thus described. The moon moves rapidly 
among the stars. Suppose that for a given instant of Greenwich 
