Still, those who cannot sympathize with the pure love of knowledgefor its own sake--one of the highest and noblest of human aims--should remember that astronomy is also of immense practicalimportance to mankind, and especially to navigation and commerce.Unless great astronomical calculations were correctly performed atGreenwich and elsewhere, it would be impossible for any ship orsteamer to sail with safety from England to Australia or America.Every defect in our astronomical knowledge helps to wreck ourvessels on doubtful coasts; every advance helps to save the livesof many sailors and the cargoes of many merchants. It is thispractical utility of astronomy that justifies the spending ofnational money on observatories and transits of Venus, and it isthe best apology for an astronomer's life to those who do notappreciate the use of knowledge for its own beauty.