292 ' On the Rapid Production of Steam. 



60"^ ; the existence of a lofty and unbroken chain of mountains, be- 

 tween us and the Pacific ; and finally, upon our position on the east- 

 ern instead of the western side of the continent. It has been sup- 

 posed by some, that our climate will be greatly improved, when the 

 country shall have become, to a more considerable extent, disforest- 

 ed. ' The progress of cultivation may have some influence upon it, 

 but it must be remembered that the climate of China, the most dense- 

 ly populous country in the world, continues to bear an intimate re- 

 semblance to our own, and it is strongly suspected, that unless the 

 direction of the great aerial currents, that traverse the surface of the 

 earth, shall be permanently changed, the Rocky Mountains melted 

 away, or the territory of the United States transferred to the western 

 side of them, our climate will be much the same a thousand years 

 hence that it is now. 



Art. VII. — Observations and Experiments on the rapid production 

 of Steam in contact with metals at a high temperature; by Wal- 

 ter R. Johnson, Professor of Mechanics and Natural Philoso- 

 phy in the Franklin Institute, Philadelphia. 



To account for the sudden explosions which sometimes occur in 

 steam boilers, one hypothesis assumes that the metal, by undue ex- 

 posure to the fire, and by a deficiency in the supply of water, be- 

 comes intensely heated and thereby affords a source of heat ready to 

 act with great rapidity on any new portion of water which may be 

 injected, or otherwise brought into contact with the heated surface. 

 Whether the water be thrown up by ebullition, or caused to flow over 

 the hot part of the boiler, by some change in the position of the lat- 

 ter, will be of litde consequence to the result so long as we are sure 

 of the presence of the dangerous generator. 



The construction of many steam boats, or rather the arrangement 

 of their boilers, favors the presumption that a mere change of posi- 

 tion has sometimes caused an explosion of the nature now alluded to. 



In the boats which navigate our western waters, eight or nine boil- 

 ers of a cylindrical form, thirty inches in diameter, and about four- 

 teen feet lon^, are laid side by side lengthwise of the boat, so that, 

 allowing for interstices, from twenty two to thirty feet of the breadth 

 of the deck, are taken up by the aggregate diameters of the row of 

 boilers. They are almost uniformly constructed with returning flues 

 from nine to twelve inches in diameter. 



