HEALE.— On Moon Occultations. 61 
I have here the computations of five occultations which I have observed 
with a portable telescope at different times without any special care. Of these 
four agree with one another within a maximum of seven seconds ; the fifth is 
apparently affected by some blunder, as it varies upwards of twenty seconds 
from the others, but, as even this discrepancy is only about four and a-half 
statute miles, it might be considered accurate in comparison with the 
approximations generally available on board ship. 
The calculation of longitude from the observations is, it will be observed, 
not by any means formidable for its length, and it presents no intricacies 
which an ordinary navigator may not easily master. 
