He also published an influential textbook on telegraphs, and worked in British India at a senior post in the Telegraph Department. He was involved in setting up telegraphic communication between Agra and Calcutta solving problems in transmission of submerged cables. He was commissioned by the Railways to perform a feasibility study of lighting Indian Railway stations by electric lamp.
In 1867 a zoo was proposed by Joseph Fayrer and the idea was again raised by Schwendler in 1873. He helped in the setting up of this garden and offered his small menagerie (prior to his leaving India) to create the nucleus of the Alipore Zoological Gardens in Kolkata. A memorial was erected at the zoo premises in 1883.