164 
HINTS TO TRAVELLERS, 
ii. M. s'. 
Watch showed at time of observation of occupation about io p.m. 9 1 50 
h. m. s. 
Error of Watch on 24th.= 1 14 23 
2*6 days’ rate =2 28-i secs, losing. 28-1 
Error of Watch at time of occupation. 1 14 51*1 .. 1 14 51*1 
True time at observation, 26th 10 16 41*1 
Longitude by Meridian Distance . 
The difference of longitude of two places is the difference of time 
Between them at the same instant. 
If therefore you can transport the time at one place, by means of a 
watch, to another place, and obtain the true time at that second place, the 
difference of those times is the difference of longitude between the two 
places.. 
This is accomplished in practice, by finding the errors of the watch at 
the two places, either by absolute, or equal altitudes, and the rate, in any 
case at one of them, though it is better to find it at both, and take the 
mean. 
Bules.—T he time at the place where the first observations were taken 
must be reduced by the mean rate and the interval to the same instant 
of time as when the observations were taken for error at the second place 
of observation. This is done by multiplying the mean rate by the interval 
of time (expressed in days and decimals of a day) that has elapsed between 
the last observation for error at the first station, and the first observation 
at the last station. 
Error sloiv. —Suppose a case where the error of the Watch at both 
stations was found to be slow on the local time, then, after reducing the 
error of the watch, as above, from the first station to the second, if the 
watch is less slow at the second station, the meridian distance will be 
West, because we have, by travelling to the West, reduced a slow error 
on the local time of the first station. On the other hand,'if the error 
at the second station, after the above reductions, should be more slow, 
then the meridian distance will be East, because by travelling East we 
have increased a slow error on the local time of the first station. 
Error fast .—If the error of the watch at both stations is fast, then 
(after reducing the time of the first station to the second station, as 
directed above) if the watch is less fast at the second station, the 
