From Introduction: "A summary of the tests made at St. Louis and a resume of the conclusions to be drawn from the tests and from the opinions of gas-producer manufacturers on the status of the gas producer and gas engine was published in a Survey bulletin in 1907. As it is desirable to repeat much of the material that appeared in the former bulletin (now out of print), this presentation may be regarded as a revision of the previous one, although considerable information not previously available for publication has been added."