ENGINEERING. 583 



UTILIZATION OF SOLAR HEAT. 



Reports from the Paris Exhibition bring us some interest- 

 ing statements concerning M. Mouchot's persistent and laud- 

 able efforts to perfect an apparatus for utilizing the solar 

 heat for the preparation of food, distillation of alcohol, etc., 

 and as a motive power. From published accounts, he has 

 been able, to a notable extent, to perfect his apparatus for 

 these purposes. He has succeeded, we are told, with the aid 

 of a mirror less than one fifth of a square meter, in roasting a 

 pound of beef in twenty-two minutes, in completing a stew 

 in an hour and a half that required four hours with a wood 

 fire, and in raising to the boiling-point in half an hour three 

 quarters of a litre of cold water. For producing power, M. 

 Mouchot employed a conical solar receiver, the mirror of 

 which had an aperture of twenty square meters, in the focus 

 of which is located an iron boiler, weighing, with accessories, 

 200 kilograms (1 kg=2.2 lbs.), and having a capacity of 100 

 litres (1 litre = 1.05 quarts). On September 2 this appara- 

 tus was put in operation, and in half an hour the water was 

 raised to boiling, and ultimately a pressure of six atmos- 

 pheres was obtained. On September 29 a pressure of seven 

 atmospheres was obtained in two hours, notwithstanding 

 several passing clouds. The solar engine has for a number 

 of years been made the subject of special study by engineers 

 of eminence (Ericsson among the number), and if ever ulti- 

 mately perfected, it may attain to a position of great impor- 

 tance in countries where the uniform intensity of the solar 

 heat throughout the greater part of the year is now regard- 

 ed as a misfortune. The probable development of this form 

 of motor may, however, be regarded as highly problematical. 



STEAM ROAD -WAGONS. 



Some attention was drawn during the summer of 1878 by 

 the trial-tests of steam road-wagons, in competition for the 

 prize of $10,000 offered by the Legislature of the State of Wis- 

 consin. Two machines appeared as contestants, but only one 

 was able to go through the prescribed conditions of perform- 

 ance. This wagon made the trip from Green Bay, by way 

 of Beloit, to Madison, over the common high-road, a distance 

 of 201 miles, at an average speed of six miles an hour, draw- 



