65Where a deficiency in the amount realized from an assessment in any class is caused by the failure of some of the employers in that class to pay their share of the assessment, or by any disaster or other circumstance that in the opinion of the Commission would unfairly burden the employers in that class, the deficiency or loss may be made up by supplementary assessments upon the employers in all the classes, and the provisions of sections 59 to 62, so far as applicable, shall apply to such assessments.