Any person, firm or corporation engaged in any manufacturing or mechanical business may contract with adult or minor employees to give one week's notice of intention on such employee's part to quit such employment under a penalty of forfeiture of one week's wages. In such case, the employer shall be required to give a like notice of intention to discharge the employee, and on failure, shall pay to such employee a sum equal to one week's wages. No such forfeiture shall be enforced when the leaving or discharge of the employee is for a reasonable cause. The enforcement of the penalty shall not prevent either party from recovering damages for a breach of the contract of hire.