Elliott Perkins, master of Lowell House, gave the first specific clue yesterday to the origin of a series of explosions which rocked the House Saturday night.

In an open letter to the members of the House, entitled "Cannon Crackers," Mr. Perkins commented that "throwing these things is downright dangerous."

The letter admitted, however, that such operations were "intensely interesting to those of an intellectual maturity below 16 years and two months," and that the first individual found "making a dangerous nuisance of himself can expect expulsion from the House."

Sources close to the Housemaster last night were unusually quiet.