At the time that this engine was being developed it was practically impossible to obtain any outside information regarding the proper way of constructing it. The little that was then known had been learned through laborious experience and at great cost by the experimenters who were attempting to build automobiles, and was zealously guarded in the hope of preventing their rivals from utilizing the results of their labors. It was the known custom, however, of all engine builders at this time to use a separate spark coil and a separate contact maker for each cylinder of an engine, no matter how many cylinders there were. This multiplication of the spark coils, which at that time were very heavy, not only added greatly to the weight but also had the same defect that the wipe-spark type of sparking arrangement had of being exceedingly difficult to so adjust that all of the contact makers would perform their functions at exactly the same point in the cycle for each cylinder. To obviate these difficulties, both of adjustment and of excessive weight, the writer devised what is supposed to have been at that time a new and valuable multiple-sparking arrangement whereby only one battery, one coil and one contact maker were utilized for causing the spark in all five cylinders, a small commutating arrangement in the high-tension circuit distributing the sparks to the proper cylinders at the proper time. This form of sparking arrangement was found upon test to work so satisfactorily that it was afterwards adopted for the small engine of the quarter-size model, and also for the new and larger engine which was afterwards built and which will be described further on. It is needless to describe in detail the many and perplexing difficulties which were experienced in procuring suitable spark coils, spark plugs and other appurtenances of the sparking apparatus, all of which at this time were in a very crude state of development, there being only a few different makes on the market, and most of these being very unsatisfactory. One important minor improvement connected with the spark plugs may be described, as the beneficial effect produced by it was so very great that its use was continued in all future spark plugs for all of the engines. This improvement, however, is now incorporated in many of the plugs which are on the market, and in some cases patents, covering the particular form in which the improvement is incorporated, are exploited by the manufacturer. Considerable difficulty was at first experienced with the spark plugs from a coating of soot (resulting from the incomplete combustion of the gas and oil in the cylinder at the time of explosion) which formed on the porcelain and thereby caused a short-circuit, preventing the plug from working properly. This was overcome by extending the metal portion of the plug for some distance into the cylinder, and for something like three-quarters of an [p222] inch beyond the end of the porcelain insulator.