Complex sentence: Myer's Civil War innovations included an unsuccessful balloon experiment at First Bull Run, and, in response to McClellan's desire for a Signal Corps field telegraph train, an electric telegraph in the form of the Beardslee magnetoelectric telegraph machine.
Split into simpler sentences: Myer's Civil War innovations included an unsuccessful balloon experiment at First Bull Run. In response to McClellan's desire for a Signal Corps field telegraph train, an electric telegraph in the form of the Beardslee magnetoelectric telegraph machine.