paraffin oil, being the oil obtained direct from the destructive
distillation of shale in retorts; (2) green paraffin oil, which is
yielded by distilling or re-running the crude paraffin oil, and
removing the lighter or more inflammable portion by fractional
distillation; and (3) blue paraffin oil, which is obtained by
rectifying the twice run oil with sulphuric acid and soda, and
distilling off the paraffin spirit, burning oil, and intermediate oil,
and freezing out the solid paraffin as paraffin scale. The best
practical trials were obtained in Pintsch's apparatus and in Keith's
apparatus.

After describing both of these, Dr. Macadam went on to give in great
detail the results obtained in splitting up blue paraffin oil into gas
in each apparatus. He then said that these experimental results
demonstrated that Pintsch's apparatus yielded from the gallon of oil
in one case 90.70 cubic feet of gas of 62.50 candle power, and in the
second case 103.36 cubic feet of 59.15 candle gas, or an average of
97.03 cubic feet of 60.82 candle power gas.

In both cases, the firing of the retorts was moderate, though in the
second trial greater care was taken to secure uniformity of heat, and
the oil was run in more slowly, so that there was more thorough
splitting up of the oil into permanent gas. The gas obtained in the
two trials was of high quality, owing to its containing a large
percentage of heavy hydrocarbons, of which there were, respectively,
39.25 and 37.15 per cent., or an average of 38.2 per cent., while the
sulphureted hydrogen was nothing, and the carbonic acid a mere trace.
Besides testing the gas on the occasion of the actual trials, he had
also examined samples of the gas which he had taken from various
cylinders in which the gas had been stored for several months under a