— The thirty days notice was a requirement of law. It was therefore an official act, an act' involving the exercise of impartiality in the selection of the time and place of hearing. The law contemplated that the oath would be a guaranty for their impartiality, as well in selecting the time and place, as in any other part of their doings.

Such a guaranty the respondents were entitled to, and they were deprived of it, for the selection of the time and place was made when no oath had been taken.

Exceptions overruled.