Chinese recruitment on CPRR

From: "Bill George" w_george1@msn.com

Does anyone have information on the Central Pacific, or its agents, procuring labor directly from China to build the railroad? I found an entry about a Dutch Sea Captain named Cornelius Koopmanschap who ran a shipping line between Hong Kong and California, transporting Chinese workers.

Daily Alta California, Volume 21, Number 7073, 1 August 1869:

Cornelius Koopmanschap in Hong Kong has employed its scores of brokers in each Chinese province gathering together ship-loads of laborers, and its house in San Francisco has received by its own line of vessels its thousands of laborers, assigned them their masters, purchased their food, and secured for them their pay. By the aid of houses the Central Pacific Railroad has been constructed six years earlier than would have been possible without the services of the Chinese laborers ...

Is there other (primary source) documentation? ...

—Bill George