cook must be very unlucky if he cannot pick out fifteen or twenty which will do for serving up.
Another approved receipt, when the observations to be used will not come within the limit of accuracy, which it has been resolved they shall possess, is to calculate them by two different formulæ. The difference in the constants employed in those formulæ has sometimes a most happy effect in promoting unanimity amongst discordant measures. If still greater accuracy is required, three or more formulæ can be used.
It must be admitted that this receipt is in some instances rather hazardous: but in cases where the positions of stars, as given in different catalogues, occur, or different tables of specific gravities, specific heats, &c. &c., it may safely be employed. As no catalogue contains all stars, the computer must have recourse to several; and if he is obliged to use his judgment in the selection, it would be cruel to deny him any little advantage which might result from it. It may, however, be necessary to guard against one mistake into which persons might fall.
If an observer calculate particular stars from a catalogue which makes them accord precisely with the rest of his results, whereas, had they
