Under what terms is the central pacific railroad company of california authorized to build a railway headed east?

According to the terms of the pacific railroad act two companies were given authority to continue the construction of the railroads the Central pacific railroad company would start building from Sacramento heading to  the east across sierra, Nevada and the Union pacific railroad would build westward.

Explanation:

Central pacific railroad company was chartered first by the united states congress to build its transcontinental railroad from Sacramento to heading to the east.  The Central Pacific would be dominated by the “Big Four” who were the major business men who had no experience about construction of railway projects.

They borrowed heavily to finance the projects and utilized  all the loopholes of the constitution in order to gain funds for completing this project.