. PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 579 



\ places be used. By inserting different sets of wheels in two of the vertical 

 columns, the computation can be made by the sexagesimal system; that is, 

 the results will at once be converted into degrees, minutes and seconds. 



It is found, from our own work as well as that previously done with the 

 machine, that it is occasionally liable to an accidental error, from the fail- 

 ure of one or more wheels to perform its ollice, Tliese errors are purely 

 mechanical, and are not to be confounded with the principles on which the 

 machine is constructed. The question naturally arises, can these errors 

 be obviated ? The thorough examination of the source and cause of the dif- 

 ficulty leads us to conclude that by a slight addition to the mechanism, the 

 possibility of accidental error from this source may be reduced to so small 

 a limit as to make the machine perfectly reliable for any computations in- 

 chidcd within its capacity. 



Tlie success of our improvements has been satisfactorily demonstrated in 

 the use of temporary mechanism constructed for the purpose. It was found 

 that those wheels which before were frequently liable to error, worked per- 

 fectly after the proper mechanism was applied. 



"We propose to apply motive power to the machine, so that when once 

 set, it shall be a complete automaton, making its computations without the 

 assistance of any person. As soon as one set of constants are exhausted, 

 tiie machine will stop, and will also be made to give notice of the fact by 

 ringing a bell; upon which a new set of constants may be introduced, and 

 the computations continued. 



The following interesting items of scientific news were then presented 

 by the chairman : 



A New America:n Silk-Worm. 



Mr. L. Trouvelot, of Medford, Mass., has been engaged for several years 

 in rearing the altacus polyphenus, and in preparing from its cocoon a silk 

 having great lustre and strength, and superior to all other silks except the 

 best Chinese. The insect is found throughout the iSorthern States, and 

 feeds upon the leaves of the oak, maple, willow and other common forest 

 trees. Mr. Trouvelot has now seven wagon-loads of cocoons, the entire 

 progeny of which he proposes to raise during the coming summer. For 

 opening this new and important field of industry, this gentleman is entitled 

 to the thanks of all wjio are interested in the increase of our domestic 

 manufactures. 



A Buried City. 



It is said that a photographer, who has been employed by the Dutch 

 Government to take views of the most beautiful points on the Island of 

 Java, has discovered an entire city buried beneath the lava of a volcano 

 close by, which has been extinct for several centuries. 



Steam Engines in France. 

 In 1850 there were in all France but 6,832 steam engines ; in 1860 there 

 were 22,516, representing a force of 617,890 horse-power. Certain restric- 

 tions have lately been removed by the government which will doubtless 

 result in greatly increasing the number of steam engines in Ihat country. 



