НЕАгЕ.—Олп Moon Occultations. 57 
considerable amount of raw material could be obtained at small cost, to the 
joint benefit of the agriculturist and the manufacturer. Wrapping paper has 
long been manufactured by the Americans from the flowering sheaths of maize, 
but this material could scarcely be obtained here in sufficient quantity to be 
made available by the manufacturer. 
Art. XL— On the Prediction of Occultations of Stars by the Moon. 
By T. HEALE. 
[Read before the Auckland Institute, 10th November, 1873.] 
Att the methods in use for ascertaining the longitude, independently of 
chronometers, depend upon the observation of the moon's position at a certain 
instant of time at the place, then ascertaining from the tables of the moon in 
the nautical almanac, or other similar publications, the instant of time at 
Greenwich, or other standard position, at which she reaches that point. The 
difference between the two times so obtained is the difference of longitude 
between the two places. 
The most complete, as well as the most simple, method of making this 
comparison, and the one almost invariably used for observatory purposes, is 
to note the exact time of the moon’s crossing the meridian of the place by the 
transit instrument, taking, at the same time, her zenith distance, or not, 
according to the instrument employed. 
But to effect this in at all a satisfactory measure requires an observatory 
and fixed instruments of an expensive character, and accurate observations 
kept up for a considerable period and elaborately reduced by computation. 
It is, therefore, inapplicable to the purposes of a traveller, either by sea or 
land. The method chiefly employed when an approximate result has to be 
obtained from a single set of observations, is by observing the moon's angular 
distance from the sun, a planet, or a fixed star, commonly called lunars. 
The chief objections to this method depend on the circumstance that 
since the moon at fastest moves only about 1 second to 24 seconds of longitude, 
and ordinarily much less, every second of error in the angular measurement 
roduces an error about thirty times as great in the longitude ; and as the 
observations have often to be taken in very inconvenient postures, in which 
only light instruments held in the hand are available. On board ship accuracy 
cannot, as a rule, be expected from them, and in practice they are now but 
little used—far less frequently, as far as my observation goes, than they used to 
be forty years ago, though the trouble of computing them has been greatly 
lightened by special tables. 
The only remaining method of importance is by occultations of fixed stars, 
H 
