Section 17. That from and after the first day of July next, all stock brokers and bill brokers shall be required to pay the additional sum upon each license of fifty per cent., and exchange brokers one hundred per cent. upon the amount which they are required to pay by the act of twenty-seventh May, one thousand eight hundred and forty-one, entitled "An Act to authorize the licensing of stock brokers, exchange brokers and bill brokers, and to regulate contracts for the purchase and sales of loans and stocks."