The machine ahead was going at terrific speed, and the _Bertha_ for a time had all she could do to keep in sight of her. At that time it was not a question of overhauling their quarry. The plucky little _Bertha_, however, clung tightly to the chase, and Ben saw crags, canyons, shelves of rock, and grassy valleys go whirling under his feet as one watches a swiftly flying landscape from the window of a mile-a-minute train. All through the exciting flight Carl kept his glass in use. He searched the sea, now plainly visible to the west, the green landscape to the east, and the rocky summits to the north and south but for a long time, caught no glimpse of what he sought. After the chase had continued a couple of hours the boys felt the machine sinking beneath them. They both knew that there could be no good reason for this, as everything had been in working order only a short time before. Ben examined the mechanism as carefully as he could from his seat and Carl glanced apprehensively at the tanks. Their judgment told them that everything about the flying machine was exactly as it should be, and yet she kept dropping down without any apparent reason. Straight ahead was a level summit comparatively clear of rocks. Realizing that something must be done at once, Ben shut off the motors and volplaned down. The machine sank faster and faster, and the boys looked at each other with frightened eyes. It seemed as if the machine must fall short of the summit! CHAPTER XVI. THE INSIDE OF A JAIL. As has been said, it was morning when Havens caught sight of the pretty little city of Monterey on the Pacific coast. He had traveled steadily all night, and was very tired, so he decided to drop down near the town and rest during the day. Remembering the instructions he had given to the boys, he had no thought of seeing either the _Louise_ or the _Bertha_ in the air at that time. The young millionaire had made a very swift flight across the continent. It will be remembered that he had left New York city something like twenty-four hours after the departure of the boys. The _Bertha_ and the _Louise_ had spent fully twenty-four hours at St. Louis waiting for some news of the _Ann_. On the morning when Havens alighted a short distance from Monterey, the Flying Machine Boys had been on the coast something like twelve hours. It will be understood, therefore, that the _Ann_ had followed not far behind the _Louise_ and _Bertha_. While the young millionaire was sleeping at a neat hotel, after breakfast and a refreshing bath, Ben and his chums were discussing the situation in the little grass bowl into which they had dropped the machines during the dark hours.