Sadler is born near Dublin on October 17, 1796, the son by a second wife of James Sadler, one of the earliest British balloonists. The elder Sadler makes his first ascent on May 5, 1785, in company with William Windham, the politician, who subsequently consents to stand godfather to his son. In October 1811 he makes a rapid flight from Birmingham to Boston, Lincolnshire, in less than four hours. Less successful is his attempt to cross the Irish Sea on October 1, 1812, when he ascends from the lawn of the Belvedere House, Dublin, receiving his flag from the Duchess of Richmond. In spite of a tear in the balloon fabric, which he partially repairs with his neckcloth, he nearly succeeds in crossing the Channel. However, when over Anglesey a strong southerly current carries him out to sea, and he has a most perilous escape, being rescued by a fishing craft, which ran its bowsprit through the balloon. He is not deterred from making other ascents, and his name is long familiar in connection with ballooning. George III takes a special interest in his ascents.
The younger Sadler is brought up as an engineer, acquires a good practical knowledge of chemistry, and enters the service of the first Liverpool gas company. He gives up his employment there for professional aërostation, with which, upon his marriage in 1819, he combines the management of an extensive bathing establishment at Liverpool.
Sadler’s most notable feat is performed in 1817, when, with a view to carrying his father’s adventure of 1812 to a successful issue, he ascends from the Portobello barracks at Dublin on June 22. He rises to a great height, obtains the proper westerly current, and manages to keep the balloon in it across the St. George’s Channel. In mid-channel he writes, “I enjoyed at a glance the opposite shores of Ireland and Wales, and the entire circumference of Man.” Having started at 1:20 PM, Sadler alights a mile south of Holyhead at 6:45 PM.
On September 29, 1824 Sadler makes his thirty-first ascent at Bolton. He prepares to descend at dusk near Blackburn, but the wind dashes his car against a lofty chimney, and he is hurled to the ground, sustaining injuries of which he dies at 8:00 on the following morning. He is buried at Christchurch in Liverpool, where he was very popular. He well deserves the title of ‘intrepid’ bestowed on his father by Erasmus Darwin, but he did little to advance a scientific knowledge of aërostation by making systematic observations.