§ 30. Continuation of salaries of local and state welfare employees receiving training for the better performance of their duties. Subject to the approval of the department, the board of supervisors of a county and the appropriating body of a city or town may include in its appropriations moneys for the continuation of the salaries of their local welfare employees who are on leave receiving additional training for the better performance of their duties, provided that no such salaries shall be so continued to a greater extent than will reimburse such employee for the loss of earnings while on such leave. Salaries of the employees of the department may be continued in a similar fashion.