looking for McCarthy's who came to Canada mid 1850s

Hi Jane

Thank you for your query.  It is helpful to include what sources you have used to research your family up to this point. Including this information makes it easier for our volunteers to advise and assist you.
I recommend that the first place you look now would be emigration records. Generally more information was given at the port of arrival rather than the port of departure. If you knew which city they arrived at (e.g. Liverpool, New York, etc.), this could be a good place to find more information. -And perhaps even find out an exact place of origin.

Ellis Island: http://www.ellisisland.org/search/passSearch.asp

Castlegarden: http://www.castlegarden.org/

US National Archives/Immigration info: http://www.archives.gov/research/immigration/

The Boston Pilot; From October 1831 through October 1921, the Boston Pilot newspaper printed a ?Missing Friends? column with advertisements from people looking for ?lost? friends and relatives who had emigrated from Ireland to the United States. This extraordinary collection of 40,743 records is available here as a searchable online database, which contains a text record for each ad that appeared in the Pilot. http://infowanted.bc.edu/

They may have departed from cork but stopped at an English port to change ship.If you do not find a record for them in emigration records having departed from Cork  you should also check the UK records for listing of passengers.

http://www.nationalarchives.gov.uk/records/looking-for-person/

On finding their place of origin in Ireland you should then search church records. Firstly do you know what the religious denomination of your family was? you can view what Roman Catholic records exist for various parishes through the link below: 

http://www.irishtimes.com/ancestor/  (Browse Roman Catholic Parish Map)

For Church of Ireland records see: http://ireland.anglican.org/about/42 and http://www.nationalarchives.ie/.  The Anglican Record Project is has created an index to their records: http://ireland.anglican.org/cmsfiles/pdf/AboutUs/library/AngRecord/bunclodyunionindex.pdf

Accessing church records may lead to making a connection with relatives that are still living  in the same area
Here are some other websites that may be of help to you:

http://www.collectionscanada.gc.ca/index-e.html

http://www.irishtimes.com/ancestor/browse/

http://www.nationalarchives.ie/genealogy1/genealogy-records/introduction/

http://www.nli.ie/en/family-history-introduction.aspx

http://ifhf.rootsireland.ie/?gclid=CKLT_Pa4wrUCFYUf4Qod4EoAGg

We hope that this information is of help to you Jane. Please do not hesitate to contact us again.

Kind regards,                    

Genealogy Support