856 Transactions of the American Institute. 



somewhat in the water, and the proportionate resistance decreased. 

 He (Emery) had seen similar results in small vessels in the navy. 



Dr. Yan der "Weyde corroborated this by saying that the same had 

 been found true in France. It had also been found that by lengthen- 

 ing the boats the relative resistance was decreased. 



A member explained that the hulls of vessels are now made so that 

 the portions ordinarily immersed divide the water and force it later- 

 ally, while the upper portion of the same is made scow-shaped so as 

 to lift upon the waves. This is true of ocean steamers ; river steamers 

 are made with fiat bottoms. 



Safety Explosives. 

 Some time ago Ehrhardt patented several compositions which only 

 became explosive when two of tliem were thoroughly mixed, but the 

 explosive materials employed seem to have prevented their practical 

 use in the manner proposed. Quite lately Dr. Nisser has done some- 

 thing in the same direction. He prepares two compositions, one con- 

 taining chlorate of potash and nitre, and the other sulphur woody 

 fiber, and carbon in some cheap form. These powders are non-explo- 

 sive while apart, but when required for explosive purposes, they are 

 sifted together, and the resulting composition is found by experiment 

 to generate a force about four times as great as that of ordinary 

 blasting powder. It is said a saving in expense, as well as a decrease 

 of danger is secured by the employment of the new preparation. 



Revolving Tukkets. 

 The king of Prussia recently inspected the revolving turrets erected 

 on the banks of the Rhine to protect Coblenz against the attacks of 

 gunboats. " It is lamentable," says The (Britisli) Army and Navy 

 Gazette^ " that although England gave birth to the idea, we are at 

 this moment without a single revolving turret in position on shore. 

 Wliat are our royal engineers doing ? Echo answers that they are 

 conducting experiments at Shoeburyness which have as yet been pro- 

 -ductive of no practical results to ourselves, while foreigners, eagerly 

 watching all that has taken place, liave returned home with valuable 

 ideas gathered therefrom at the expense of the British nation, and 

 have erected works, and prepared for all emergencies, while we, who 

 are preeminently tlie iron manufacturing nation, have been discussing 

 plans and producing — Gibraltar shields." The Gazette is mistaken 

 as to the origin of the revolving iron turret. It was jfirst brought out 

 and patented many years ago by Tiiiiby, an American inventor. 



