As a solution of this problem, he lays down a special normal _time_ labour-day and normal _work_ (amount of work) labour-day, by considering which two factors he proposes to arrive at a unit of normal labour which shall serve as a common basis of measurement. In order to bring about the participation of all workers in the nett result of national production in proportion to their contribution to it--hence without keeping down the better workers to the level of the worst, and without endangering productivity--it is necessary, Rodbertus holds, to reduce to a common denominator the amounts of work performed by individual workers, which vary very considerably both in quantity and quality. By this means he thinks we shall be enabled to establish a fair relation between work and wages. The normal _time_ labour-day is to furnish us with a simple measurement of the product of labour in different occupations or branches of industry; and the normal _work_ labour-day is to give us a common measure of all the varying amounts of work performed in equal labour time by the individual workers. He points out that astronomically equal working time does not mean, in different industries, an equal out-put of strength during an equal number of hours, nor an equal contribution to society. Therefore the different industrial working-times must be reduced to a mean social working time: the normal _time_ labour-day. If this amounts to 10 hours, 6 hours work underground might equal 12 hours spinning or weaving work. Or, which would be the same, the normal _time_ labour-day would be 6 hours in mining, and 12 hours in textile industries; the hour of mining work would be equal to 1-2/3 hours of normal time, the hour of textile work would be equal to 5/6 hour of normal time. The normal _time_ labour-day would serve to determine periodically the proportionate relations which exist between the degrees of arduousness in labour of different kinds, with a view to bringing about a just distribution of the whole products of labour according to the normal proportional value of its out-put in each kind of employment, in each department of industry, such proportional value being determined by means of the normal time measure. Also it would lead to the fair award of individual wage, for if any one were to work only 3 instead of 6 hours in coal mining, or only 5 hours in weaving or spinning, he would only be credited with and paid for half a day of normal working time.