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Although the proper timing of the spark is as essential as the spark itself and the electrical and mechanical devices for producing the spark have been many, little attention has been given to the study of spark-advance. An error in timing of ± 20 deg. in a low-compression engine, or of ± 15 deg. in most other engines, has been shown experimentally to cause a loss of 10 per cent from the best power and economy, provided other conditions remained the same. Hand or semi-automatic control can average hardly closer than ± 15 deg. to the correct advance because the speed and the load combinations are constantly changing on the road. Two important phases mark the spark-advance problem.

The author discusses commercial-airplane design in general terms, considering the subject under the main divisions of economy, safety, speed and comfort. Under economy, mention is made of possible reductions of first cost by designing for long life and reliability, the effect of the former on the depreciation allowance being obviously advantageous. Airplane size is debated also, the trend of progress being seemingly toward the giant airplane. Safety is stated to be dependent upon reliability, structural strength, stability, control, fire prevention and reduction of risk of injury to passengers in the event of a crash. Minimizing the results of a crash is considered suggestively. Speed is governed almost solely by the ratio of wing loading to power loading; hence, speed will always be kept as low as possible without loss of business to competing transportation enterprises. Included among desirable measures to secure comfort are adequate ventilation and the elimination of noise.

Flame propagation has received much attention, but few results directly applicable to operating conditions have been obtained. The paper describes a method devised for measuring the rate of flame propagation in gaseous mixtures and some experiments made to coordinate the phenomena with the important factors entering into engine operation; it depends upon the fact that bodies at a high temperature ionize the space about them, the bodies being either inert substances or burning gases. Experiments were made which showed that across a spark-gap in an atmosphere of compressed gas, as in an engine cylinder, a potential difference can be maintained which is just below the breakdown potential in the compressed gas before ignition but which is sufficient to arc the gap after ignition has taken place and the flame has supplied ionization. These experiments and the recording of the results photographically are described.

The adoption of the present system of feeding a number of cylinders in succession through a common intake manifold was based upon the idea that the fuel mixture would consist of air impregnated or carbureted with hydrocarbon vapor, but if the original designers of internal-combustion engines had supposed that the fuel would not be vaporized, existing instead as a more or less fine spray in suspension in the incoming air, it is doubtful that they would have had the courage to construct an engine with this type of fuel intake. That present fuel does not readily change to hydrocarbon vapor in the intake manifold is indicated by tables of vapor density of the different paraffin series of hydrocarbon compounds.

THE rapid development of heavy-duty trucks and farm tractors has made it necessary for manufacturers of engines used in such automotive apparatus to face problems regarding which there is no past experience to fall back upon. The necessity in both types of engine for maximum strength in all parts carrying excessive loads constitutes a problem of great importance, but in addition to it are others of the proper utilization of fuels at present available, lubrication under excessive load conditions over long periods of time; and, of nearly as much importance, the relation of fuels to lubricants and the effect of fuels upon lubricants. Moreover, information is to be acquired regarding the value of prospective fuels as power producers, the effects they have upon engines, lubricants, etc., comparisons of cost and the like. The tests recorded in the paper were made in an endeavor to ascertain some of these unknown values.

THE production of gasoline in this country could be increased through the following changes in refinery practice: (1) Universal adoption of a high “end-point,” or upper volatility limit for gasoline (2) General use of more efficient distillation methods and equipment (3) Recovery of gasoline now lost in refinery operation (4) Wider use of cracking processes Other possible methods of increase are not considered of sufficient importance to merit discussion in this connection. Some of the details of the four methods of increase are discussed and it is estimated on the basis of the evidence now at hand that the maximum percentage increases in production under the four heads listed are as follows: (1) 15 to 20 per cent; (2) 10 per cent; (3) 10 per cent, and (4) 100 per cent.

The author believes that an incompatibility exists between the results achieved in this country by the growth of the automobile industry and the almost complete lack of rational data on the most essential elements of kinetics relating to the modern automobile. He submits considerations that can be used in establishing a rational theory of spring suspension in general. A few words are devoted to the first principles of dynamics of springs, to damping, kinematic features of harmonic motion, energy consumption and shock absorbers. An introductory problem, involving an imaginary one-wheel “elemental car”, meant for purely inductive purposes, is then analyzed. Finally the main problem is presented in the form of an analysis of a skeleton-car, spring-suspended and simplified as much as possible.

The efficiency of the automobile engine, as operated on the Otto cycle, is thought by the author to be too low, and he therefore suggests a method of improving it. He considers the various losses by which heat is dissipated in internal-combustion engines and finds that the best opportunity for increasing thermal efficiency is by an increased expansion of the charge. The author suggests that this expansion be carried 50 per cent further than is ordinarily done. In order to obtain higher efficiency at part load, the suggestion is made that instead of throttling the mixture, the admission valves be closed earlier. In case the expansion is 50 per cent longer than the induction stroke and the cut-off takes place earlier as the load becomes lighter, it will be necessary to vary the fuel opening inversely with the air induced. It is suggested that the fuel valve and cut-off lever be connected together and operated by the accelerator pedal or hand lever on the steering wheel.

The author points out the diversity of opinion on what constitutes desirable car performance in the minds of engineers and of the public generally. He believes this is largely due to the great diversity of claims which have been made in advertising literature and decries the sort of tests which have been made the basis of this publicity, pointing out that a majority of them are conducted under such conditions as make it practically impossible for the car owner ever to duplicate or confirm them. The kind of an expression or test which will inform the buying public most is one which will tell what the car will do in the hands of the average owner, and define the conditions under which a demonstration of this ability can be made, such conditions to be relatively simple and easy of fulfillment.

There is opportunity for the exercise of considerable ingenuity and mechanical skill in developing automobile signaling apparatus, but the basis of any system or appliance of this nature that is destined to meet with lasting success is quite as much a matter of psychology as mechanics. No signaling apparatus can wholly succeed of its purpose unless two phases of the human equation have been properly considered. In order to serve its purpose as a warning, the signal must penetrate the wall of partial insensibility with which every human being unconsciously surrounds himself by directing his thoughts, along some particular line. Were the pedestrian fully aware of the dangers that beset him in the street, he would require no reminder of his peril. But his thoughts are elsewhere, and, for the moment, he is unconscious with respect to his surroundings.