MECHANICS AND USEFUL ARTS. 43 



England, has patented an invention which consists in so arranging the riv- 

 eted joints of boilers, and other articles of similar manufacture, that they 

 shall not run parallel to the axis, but in a line oblique thereto, the lines of 

 plates being made to run round the axis of the boiler in a helical or cork- 

 screw direction, and the joints either at right angles to one another, or vary- 

 ing from a right angle, so as to be oblique to the direction of the greatest 

 strain. " By thus placing the lines of riveted jointing oblique to the direc- 

 tion of greatest strain," says Mr. "Wright, " any given amount of such 

 greatest or lateral strain is resisted by a greater length of jointing, and 

 consequently greater number of rivets, than when such line of jointing is 

 situated parallel to the axis of the boiler ; whilst the whole length of joint- 

 ing and number of rivets in the boiler is not increased, or is increased only 

 to an inconsiderable extent." 



Mud Pockets for Steam Boilers. J. Stephen, of Glasgow, has taken out a 

 patent for the following method of constructing boilers, to collect and remove 

 the mud deposited from impure water. The boiler is formed with a narrow 

 water space division, or pocket, extending from the underside of the boiler 

 at the furnace down to and through the line of furnace bars. The water 

 space opens at its upper wide end into the bottom of the boiler, which has 

 a row of openings in its shell at that part to form the communication. The 

 boiler itself is set slightly out of the horizontal line, the furnace end being 

 somewhat lower than the reverse end. Hence the mud and deposit of the 

 water is continually directed towards the front or furnace end where it falls 

 from the boiler into the narrow bottom of the water space or pocket. The 

 part where the deposit accumulates is carried down to a short distance below 

 the furnace bars, so that the heat of the fuel cannot act injuriously upon the 

 metal of the division space, and burn it where there is no water to protect it. 

 The mud or sediment which accumulates in the bottom of the water space 

 can be removed by an instrument put in either from the interior of the 

 boiler, or through a plug way in the front end of the water space. Loose 

 deposit can, of course, bs blown out through the plug way by the steam 

 pressure of the boiler. The water space, being passed down into the furnace 

 in the centre thereof, forms the means of dividing the furnace into two equal 

 parts, so that the sections can thus be fired alternately. 



ERICSSON'S HOT AIR ENGINE. 



Ericsson's caloric motor or hot air engine, which had been nearly forgot- 

 ten by the public, and was supposed to have been laid aside as ingenious 

 but impracticable, is again brought to notice and now seems to be decidedly 

 successful. Though the principle on which Ericsson's caloric engine was 

 originally built is wholly preserved, the arrangement and mechanism are 

 entirely different the whole being reduced to a degree of simplicity never 

 before attained in any engine. 



Several cf these engines have been exhibited in New York during the 

 past summer. One, located in an office in William-street, occupies less 

 than a cubic foot of space, and is heated solely by gas. The power devel- 

 loped by it, is greater than that of an able-bodied man. It is employed in 



