have a look at http://www.ee.surrey.ac.uk/Contrib/manx/famhist/genealgy/emig.htm
the 1910 was a push/pull situation - pull by the Canadians who wanted more labour etc and pushed by the lack of jobs etc in the UK
In 1840's there was depression etc but not on the Irish scale - the emigration in 1826/7 was I think mainly socio-political in that economics were bad, the Keys and the last of the Athol's (then still governor) were at loggerheads, the Athol Bishop was attempted to exact punitive tithes etc and they were mostly Methodists who decided to move en-masse