11 June 1801 Hospital Mate.
Malta 27 Aug 1801 Hospital Mate.
Malta Nov 1801 Attached to the 2nd/63rd (West Suffolk) Regiment of Foot.
Malta 22 Apr 1802 Left for Egypt to form part of the garrison at Alexandria.
23 Apr 1802–6 May 1803 Served with the garrison in Alexandria Egypt.
Malta 7 May 1803 Returned from Egypt. Served at the military hospital Valletta.
Malta 1804 Hospital Mate at the military hospital Valletta.
Malta 28 Aug 1804 Assistant Surgeon 61st (South Gloucestershire) Regiment of Foot.
Malta 22 Sept 1805 Surgeon Garrison Battalion Sicily.
31 Oct 1805 Left Malta for Calabria on Lt Gen Sir James Craig's Expedition to Sicily.
July 1806 Served at the Battle of Maida.
1807 Served in the Second Egyptian Campaign, under Inspector of Hospitals Ralph Green, when he sustained a shoulder wound while on a mission to the Mamelukes.
Malta 1 Mar 1808 Returned to Malta.
17 Mar 1808 Surgeon Sicilian Regiment.
11 May 1809 Surgeon 61st (South Gloucestershire) Regiment of Foot.
Malta 30 Sept 1809 Left Malta.
1810–12 Served in the Peninsular War. He was severely wounded in Portugal.
16 Apr 1812 Surgeon Staff.
1816 Awarded his MD from the University of Edinburgh where he had spent much of the previous two years preparing for the examination.
25 Jan 1816 Reduced to half-pay but returned to the service on 19 Sept 1816.
25 Feb 1818 Reduced to half-pay. Set up in practice in the Clifton district of Bristol, becoming senior physician to the Clifton Dispensary.1
1829 Physician to the Bristol Royal Infirmary.
21 Sept 1830 Retired with the rank of Deputy Inspector General. During the 1830's he was a committee member of the Bristol Institute for the Advancement of Science, Literature, and the Arts, and applied himself to develop its library and museum. he contributed to the Friends of the Established Church in Ireland, the Gloucester and Bristol Diocesan Church Building Society for new churches and chapels, the city's Magdalene House, Blind Asylum, and School of Industry.1
1832 Served as Secretary to the Board of Health in Bristol during the cholera epidemic of 1832.
In the mid 1850's, Howell retired from Bristol to Datchet, Buckinghamshire, before moving to Sicily.1