Purpose of the flight and payload description
The reference came from two old 4" x 5" acetate negative of balloons carrying cosmic ray detection equipment being released at the University of Chicago campus on October 30, 1948. In one of the images can be seen Prof. Marcel Schein posing along with an undergraduate student with the payload.
The caption of the image reads "The carrier is made of transparent material so that the (cosmic) rays can reach and be recorded on the equipment" which is not true. The reason of using transparent material was to create a "greenhouse" warming effect to protect the electronics of the harsh conditions of the stratosphere.
Details of the balloon flight
Balloon launched on: 10/30/1948
Launch site: Stagg Field, University of Chicago, Illinois, US
Balloon launched by: Chicago University Group
Balloon manufacturer/size/composition: Balloon Tandem Tandem x 21