The experiment of using iron pavement is being tried at Boston. The blocks are twelve inches in diameter, eight inches deep. one inch thick, of cast iron, cylindrical in form, hollow, and divided into cells which will be filled with gravel. The blocks are so made that when, properly laidfthe edges overlap in such a manner, as to keep the whole firmly set.— This paving is being laid merely as an expe riment, for the purpose of seeing what - effect the frost will ha ve upon it. The irritating grain of sand which, by ac cident or inCaution, has got within the shell of the oyster, incites the living animal to secrete from his' own resources the means of coating the intrusive substance and thus germinates the pearl.