The New Jersey Session Law you are looking for is available online only from the Rutgers University School of Law Camden website. It is available as part of a scanned collection of images from the original printed books. The link below will take you to the first page of the volume that contains the law. From there, use the available navigation tools to get to the appropriate chapter.
You clicked on the Laws of 1939, Chapter 309.
This law is available in the laws of the N.J. Legislature's session: 163.
CLICK HERE FOR THE SESSION LAWS.
To search the New Jersey State Library for legislative history on this law, CLICK HERE.