3 Mar 1854 Staff Assistant Surgeon.
Malta 27 Mar 1854 Arrived from England.
6 Apr 1854 Left for Turkey.
22 Sept 1854 Assistant Surgeon 23rd (Royal Welsh Fusiliers) Regiment of Foot.
Victoria Cross. On 8 and 18 Sept 1855, at Sebastopol, close to the Redan, Assistant Surgeon Sylvester went out under heavy fire with Cpl Robert Shields VC 23rd Regiment, to dress the wounds of Lt Dyneley, who lay there mortally wounded (Gazette 20 Nov 1857).
1857 Served in the suppression of the Indian Mutiny.
10 July 1860 Staff Assistant Surgeon.
15 Nov 1861 Reduced to half-pay.