Indexed Upper Canada 1842 census on FamilySearch

It isn't on Ancestry, nor online at Library and Archives Canada (mentioned as coming soon!). This would seem to be the first appearance of the indexed 1842 census of Upper Canada (Ontario) online, except for some local transcripts.
FamilySearch has indexed 20,851 records linked to original images.

Those 1,169 images can also be browsed by county/district. They are: Carleton, Bathurst; Durham, Newcastle; Gore; Grenville, Johnstown; Haldimand, Niagara; Lincoln, Niagara; London; Northumberland, Newcastle; Russell, Ottawa; Simcoe, Home; Toronto (City); Unidentified locality; York, Home.

Unfortunately not all area's records survive, and some that have published transcriptions are not in this collection.

The format is quite different from that familiar on later censuses. Only the head of household is identified by name along with quite a lot of other information about the person, his (usually) family and land. The number of family members in various age ranges are given by gender.The images, often challenging to decipher, are in a wide format spread across more than one image. Being so early they merit close study.

Start your search at http://goo.gl/TezNq