SEVERE MEASURES OF THE PHILADELPHIA POLICE. – In another column will be found a communication from the Quartermaster of the Sixth regiment New York Militia, complaining of some rough treatment which he has just received at the hands of the Philadelphia police. It appears that he was passing through that city on his way to join his regiment, when he was arrested by them, without the slightest cause, although he was in uniform at the time, and stated who he was. He was taken before the police authorities, examined, and then discharged without a word of explanation or apology. He mentions another instance in which the movements of a loyal and well disposed individual were interfered with in the same arbitrary manner. It is not many days since a body of West Point Cadets were subjected to similar harsh treatment. The police authorities of Philadelphia should recollect that, as martial law has not been proclaimed in that city, they have no right to deal thus summarily with peaceable strangers. At all events, whether acting upon information or suspicion, they are bound to make amends for the inconvenience they may cause innocent people by some little show of courtesy in the way of explanation.