MECHANICS AND USEFUL ARTS. 83 



LEONARD'S DYNAMOMETER, 



A new Dynamometer (power measurer) invented by W. B. Leonard, 

 Esq., Secretary of the American Institute, is constructed as follows : A 

 square box of cast iron, to the front and back plates of which are attached 

 links for the appliance of the machine and the power used, contains at the 

 bottom a piece of ordinary clock-work, the object of which is to give a con- 

 stant revolving motion to a circular table covered with leather. ' Near the 

 lop of the box, on either side of this revolving table, are stiff spiral springs, 

 which are fastened to the front and rear plates of the box. Directly over 

 the revolving table is a spindle, the two parts of which slide upon each 

 oilier, like a telescope, as the power applied draws out the spiral springs ; 

 and in the centre of this spindle is a brass wheel which revolves at right 

 angles with the circular travel of the table. At the extremity of this spin- 

 dle is a disc, on which revolving hands mark by proper figures the total 

 amount of strain made by the team. Now attach the team to the front link 

 and the machine to the rear one of the box. The parts are drawn asunder, 

 thus straightening out the spiral springs, pulling the sliding portion of the 

 spindle and causing the upper brass wheel to pass off of the centre of the 

 revolving table, where, of course, it previously was at rest, and to revolve 

 itself by the forward travel of the table, which it touches. As this wheel goes 

 round, it turns a pinion wheel at the other end of the spindle, and by an ar- 

 rangement of one or two cog-wheels the hands go round the disc, faster or 

 slower as more or less power is applied, and a perfectly accurate registry is 

 made of the draught of the machine attached. 



EFFECT OF THE DRAINAGE OF THE LAKE OF HAARLEM. 



The value of the land recovered by Holland from the lake of Haarlem, is 

 increasing at a rate which insures payment of all the outlay for the drainage 

 in a comparatively short time. Good crops of colza and rye have been 

 grown, and the potatoes are excellent. Two farms of considerable extent 

 are established ; two large villages are being built, and the district is trav- 

 ersed by two good roads. No ill consequences were experienced from inter- 

 mittent fevers, as was dreaded when the surface was first laid bare, and the 

 numbers of dead fish had no other effect than to fertilize the soil. No object 

 of natural history or of antiquity was discovered. Holland has now two or 

 three parishes more than she had four years ago. Leydcn and Haarlem dis- 

 puted possession of the newly Avon territory ; but the government has de- 

 cided that it shall form a district by itself. Amsterdam, relieved from the 

 danger once threatened by the meer, is laying on a supply of drinkable 

 water from the downs or sand-hills along the sea shore. It is worthy of re- 



m 



mark, that the sources in these hills, though copious and of good quality, 

 are most of them beloAV the level of the sea. 



DEADENING WALLS AND CEILINGS. 



There is no greater nuisance in modern houses than that of the transmis- 

 sion of sound through parti-walls. Any practical, inexpensive, and efficient 



