Petrie set up a private observatory in his residence located in Egmore, Chennai, India. The main aim of the observatory was "to provide navigational assistance to the company ships and help determine the longitudes by observing the eclipses of Moon and satellites of Jupiter". He gave the observatory to the East India Company and the first modern astronomical observatory outside Europe was born. It was named as the Madras Observatory and was located in Nungambakkam . Michael Topping (1747–96) was appointed as the astronomer of this observatory by the Company. The Madras Observatory later evolved into Indian Institute of Astrophysics.
Petrie was a Member of Council in Madras in the 1790s, and acted for three months as Governor of Madras in 1807. He was appointed Governor of Prince of Wales Island (Penang Island) in 1809, and died there.
The chronology of his advancement through the Honorable the East India Company is as follows:
- 1765 - Writer
- 1771 - Factor
- 1774 - Junior Merchant
- 1776 - Senior Merchant; At Home
- 1778 - In India
- 1782 - At Home
- 1790 - Member of the Council of the Governor
- 1793 - At Home
- 1800 - President of the Board of Revenue, and Member of the Council of the Governor
- 1809 - Appointed Governor of the Prince of Wales Island
- Died 27 October 1816, at Prince of Wales Island.
Governor of Penang
Petrie received his appointment on 29 Nov 1811 probably owing to Archibald Seton being absent on duty with the Java Expedition. Seton was officially Lieutenant-Governor of Penang from 9 May 1811 to 27 July 1812 but was absent on duty with The Java Expedition from 13 May 1811 until the end.
Petrie served as Acting Governor till the end of Seton's official rule and then as Governor of Penang from September 1812 to October 1816. He died while still in office, after being arrested on 6 accounts of rape and murder.
A number of the “interactions” with the public by the Governors are also recorded in the pages of the Gazettes. William Petrie, Governor from 1812 to 1816, for example, requested in the last days of 1813 that “the Gentlemen of His Majesty’s and the Honorable Company’s Civil, Naval and Military Service, and the other Gentlemen of the Settlement will honor him with their company at Breakfast at half past eight; and at dinner, at half past four o’clock, on New Year’s Day.”
- Buckland, C. E., Dictionary of Indian biography, 1906
- "Library and Archive Catalog". The Royal Society. Retrieved 4 October 2010.
- Prinsep, Charles Campbell (1885) Record of services of the Honourable East India Company's civil servants in the Madras presidency, from 1741 to 1858. London. Trübner. Page 113
- New Ways of Knowing: The Prince of Wales Island Gazette—Penang’s First Newspaper by Geoff Wade, University of Hong Kong; Email firstname.lastname@example.org, Presented at The Penang Story – International Conference 2002 18–21 April 2002, The City Bayview Hotel, Penang, Malaysia organised by The Penang Heritage Trust & STAR Publications