 The death of Henshall's mother, and his absence led to criticism from the canal company for not attending to the work.Henshall also completed the Bridgewater Canal in 1776.In December 1787, along with two other engineers, he investigated flooding on the Mersey and Irwell Navigation and noted that the navigable depth at Hollins Ferry was 2 feet to 2 feet 9 inches, whereas it had been 1 foot 8 inches sixteen years previously.