Unitil Corp. -- distributor of electricity and natural gas to Fitchburg, Ashby, Lunenburg and Townsend -- announced Thursday that higher sales and margins partially offset by higher net operating expenses drove a 7.9 percent first-quarter earnings boost over the same time last year. Unitil announced net income of $13.6 million, or $0.98 per share, for the first quarter, an increase of $1 million, or $0.07 per share, compared to the company's results for the first quarter of 2014.