Town Cancels. 
For someone who is interested in where their ancestor(s) came from, collecting town cancels can be an interesting, and, surprisingly, difficult collecting task. During and after the Famine, people from the countryside migrated to the larger cities in search of work and food. While we are well aware of families going to England, America, and Canada, we tend to forget those who got only as far as Dublin, Cork, or Belfast. Most did not return to the country since they had nothing left there. The landlords on the large estates did not need or want more tenant farmers. Land might be available for purchase, but that required money. Thus we see Ireland today with a disproportionate distribution between city and country.
This affected mail. People in the country lost contact with relations and neighbors. This is reflected in the number of letters from some of the smaller towns. My maternal ancestors were from the Ballyhaunis area of Co. Mayo. Those who had land sold it to pay for passage to the US. Those who bought it had little reason to maintain contact and, in some cases, feelings were hurt in the process, some permanently.. The town decreased in size by about 75-80%. While today there is some industry and country folk are encouraged to stay, it has only recovered a relatively small percent. Even the expansion of the nearby Shrine at Knock, there are more tourists, but little significant reverse emigration. The bottom line is that I’ve only found a few covers; however those I have, I cherish.