They lay flat under a mound. There was a small boat hidden below the far end of the island. “Get out of this if you can!” said the noncommissioned man, an electrician sergeant. “Hurry! I’ll give you five minutes! Good-by!” He crawled back into the works. As they rowed away, they saw boats with invaders leaving the mainland for the island. Then there came a lick of flame out of the mortar battery that expanded instantly into a spraying fountain. An enormous detonation nearly blew their boat out of the water. The sergeant had found the firing key and touched off the hidden mine to demolish the defenses. In the excitement over this news that had broken the dull strain of waiting, the people of Boston scarcely noticed that all at once the firing at sea had stopped. _Demanding Surrender_ Down the harbor a boat with a flag of truce was lying under Fort Warren. An officer, led blind-folded into the works, presented a summons transmitted from the headquarters of the army. It called on the commander to surrender the entire system of defenses without further damage. It demanded also that a complete diagram of all the mine fields be delivered at once. “You have four hours,” continued this summons. “At the end of that time, we shall bring our artillery to bear on the city from every quarter. Every five minutes thereafter we shall fire on a given section. You have made a brave and magnificent defense. By surrendering now, you will save your city from unnecessary destruction which you are unable to prevent otherwise.” “I will reply in half an hour,” said the commander. At the end of that time he sent this answer: “I shall surrender the defenses on condition that the city be left inviolate: that no troops occupy it: that the civil authorities be left in control: and that no levy be made on the municipality.” “Absolutely refused,” the hostile commander replied promptly. “Unconditional surrender, or bombardment begins at time stated. If any attempt is made to dismantle works, bombardment will begin at once.” This was at noon. The hour-hand of the Old South Meeting House clock had not quite touched one, when artillery was passing through Waltham and Newton Centre, and along all the roads crossing the Charles and Neponset Rivers. There were cavalry and cycle and motor troops on these roads, and trains full of infantry. But always and everywhere was artillery. The sleek guns, pounding along New England’s highways, spoke so wickedly of destructiveness, that they were more terrifying to the population than long columns of heavily armed men. At Jamaica Plain big howitzers were detrained and taken to the ridge running west by north from the line of the New York and New England railroad. More guns were unloaded in Brookline and posted on the crests from whose tops, 200 feet high, they had all Brookline, all Boston to the bay, and Cambridge and Somerville under their long range fire.[106]