which lasted for twelve hours—­that the total consumption of fuel, including that for getting up steam from cold water, was just under 1.8, actually 1.79 lb. per gross indicated horse-power per hour.  That gross indicated horse-power was obtained in a manner which it is desirable should always be employed in steamboat trials.  It was not got by using as a divisor the horse-power of the most favorable diagram obtained during the day; but it was got from diagrams taken during the regular work; then, every half-hour, when the pressure began to die down, from coal being no longer put upon the fire, diagrams taken every quarter of an hour, and then toward the last, every five minutes; and the total number of foot pounds were calculated from these diagrams, and were used to obtain the gross indicated horse-power.

Further, so far as could be ascertained by the process of commencing a trial with a known fire, and closing that trial at the end of six hours, with the fire as nearly as possible in the same condition, the consumption was 1.66 lb. of coal per gross indicated horse-power per hour.  So that, without taking into account the coal consumed in raising steam from cold water, the engine worked for 1-2/3 lb. of coal per horse per hour.  I think it well to give these details, because undoubtedly it is an extremely economical result.

ETHER ENGINE.

Our president alluded to the employment of ether as a means of utilizing the heat which escaped into the condenser, and gave some account of what was done by Mons. Du Tremblay in this direction.  It so happened that I had occasion to investigate the matter at the time of Du Tremblay’s experiments; very little was effected here in England, one difficulty being the excise interference with the manufacture of ether.  Chloroform was used here, and it was also suggested to employ bisulphide of carbon.  In France, however, a great deal was done.  Four large vessels were fitted with the ether engines, and I went over to Marseilles to see them at work.  I took diagrams from these engines, and there is no doubt that, by this system, the exhaust steam from the steam cylinder, which was condensed by the application of ether to the surface of the steam condenser (producing a respectable vacuum of about 22 inches), gave an ether pressure of 15 lb. on the square inch above atmosphere, and very economical results as regards fuel were obtained.  The scheme was, however, abandoned from practical difficulties.  It need hardly be said that ether vapor is very difficult to deal with, and although ether is light, the vapor is extremely heavy, and if there is any leakage, it goes down into the bilges by gravitation, and being mixed with air, unless due care is taken to prevent access to the flues, there would be a constant risk of a violent explosion.  In fact, it was necessary to treat the engine room in the way in which a fiery colliery would be treated.  The lighting, for instance, was by lamps external to the engine room, and shining through thick plate-glass.  The hand lamps were Davy’s.  The ether engine was a bold experiment in applied science, and one that entitles Du Tremblay’s name to be preserved, and to be mentioned as it was by our president.