Even as a professor of anatomy can reconstruct the skeleton of a prehistoric mammoth from a few scraps of bone, so can a gunnery expert decide upon the calibre and power of an unseen and unknown weapon from a few fragments of its projectile--and with a greater degree of certainty than in the case of the constructive anatomist. From available data, combined with information picked up from examination of such remains of the shells as were recovered, the experts decided that the projectile was seven feet in length with an external diameter of four inches; that the weapon was a 120-calibre gun, with a muzzle velocity of from 3000 to 3500 feet per second and with an extreme range of fifty-five miles. It was also established that at a range of twenty-five miles--the distance between the position of the submarine and the town of Portsmouth--the projectiles must have attained the extreme vertical height of eight and a half miles. In the midst of his labours, Brian Strong was called to the telephone in the Commodore's office to answer an urgent inquiry from the Admiralty. Sir John Pilrig was at the instrument, anxiously inquiring whether Mr. Strong could give him any information about the Rioguayan submarines. "I cannot," replied Brian bluntly. He was not the sort of man to beat about the bush and try to give the impression that he was in the position to supply the information. "Aircraft was my line. But my nephew here can give you particulars." Peter took his uncle's place at the telephone and described the submarines he had seen manoeuvring off San Antonio. "They were possibly instructional craft," he added. "Somewhat resembling our obsolete C class." He proceeded to describe the craft in clear technical language, which compelled Sir John to inquire in what circumstances he had gained the knowledge. "I was a sub-lieutenant, R.N., sir," he replied. "Retired under the regulations for the reduction of personnel." "Ah," commented the Deputy Chief of Staff. "Very good. I'll ring off now." Peter went back to his work. CHAPTER XXV Seaplane and Submarine Two hours after the shelling of Portsmouth by a Rioguayan submersible cruiser, Southampton was heavily bombarded, presumably by the same craft. Here, the firing was of a more concentrated nature, practically all the projectiles falling in the docks, although an obvious but unsuccessful attempt was made to destroy the Naval Ordnance Magazines at Marchwood. Southampton, however, escaped comparatively lightly--few of its prominent buildings were even damaged, and the toll of human life in the town itself was small. At the docks, too, the loss of life was not great, owing to most of the workers quickly finding cover which proved useful against anything but a direct hit. Within thirty minutes of this bombardment came telegraphic reports that Plymouth and Devonport were under hostile fire.