On the 4th of May, 1839, Perry received orders which he was glad to carry out. He was directed to give his attention to experiments with hollow shot. These were round projectiles, non-explosive, but in that line of the American idea of low velocity, with smashing power. With less weight, they were of greater calibre, and required less powder in firing. They were invented by W. Cochrane, known as the father of heating by steam, and other useful appliances. Perry selected a site near Sandy Hook and erected platforms, targets, sheds, and offices for ammunition and fuses. From this first trial and scientific study in the United States, of bombs and bomb-guns, down to the last experiments with dynamite shells, the waste space at Sandy Hook—the American Sheerness—has been utilized in the interest of progress in artillery. Perry set up butts at 800, 880, 1,000 and 1,200 yards distance from the guns, and erected one target for firing at from the ship. He devoted himself to the experiments with the best methods and instruments of precision, then at command, during the months of June and July, returning to the navy yard once or twice a week for letters, provisions and fuses. The experiments in shell practice were interesting, instructive and sufficiently conclusive. Those with hollow shot were not so satisfactory. The faith of Perry in the shell-gun was fixed. Thenceforth he believed that bombs could be fired with very nearly as much precision and safety from accident as solid shot. He saw, however, that much practice, even to the point of familiarity, was needed. His report, at the end of the season, in which he recommended a continuance of the experiments, gives us a picture of the state of knowledge in our navy at that time, concerning shell-shot. Not one of those under his direction had ever seen a bomb-gun discharged; nor had had his attention specially called to a shell-gun when in the navy, which had so long suffered from the dry rot of unmeaning routine. He complains of the lamentable want of knowledge in this important branch of the naval profession, when already so many of the French and British ships were armed with shell-guns. However, the officers trained at Sandy Hook, were now capable of teaching others in the use of explosive projectiles aboard the ship. Men and boys had all made progress in expertness. He suggested that the winter months be employed in teaching boys on the _Fulton_ a knowledge of pyrotechny, and that fifteen or twenty boys from the _North Carolina_ should be associated with them, and a class of gunners be thus trained. His plan was approved by the Department. A course of study and drill in gunnery, pyrotechny and the knowledge of the steam engine, was organized and carried out during the winter. The graduates of this school afterwards gave good account of themselves in the Mexican and our Civil War. We see in this school, the beginning of the present admirable training of our sailors in the science of explosives.