From 1914-1918.net:
1/7th Battalion
August 1914 : in Dalmeny Street, Leith. Part of Lothian Brigade, Scottish Coast Defences.
24 April 1915 : transferred to 156th (Scottish Rifles) Brigade, 52nd (Lowland) Division.
A and D Companies were involved in a rail accident at Quintinshill near Gretna on 22 May 1915 while en-route to Liverpool from Larbert in Stirlingshire. 210 men were killed and 224 injured, forming the majority of the 473 casualties of the worst disaster in British railway history.
Sailed from Liverpool 24 May 1915, going via Egypt to Gallipoli 14 June 1915.
Returned to Egypt 8 January 1916.
Moved to France, landing at Marseilles, 17 April 1918.
You should check local newspapers. There is bound to have been a story printed.
CWGC gives his parent's address.
Ken