134 ANNUAL OF SCIENTIFIC DISCOVERY. 



ought to be less disposed to rest satisfied with the progress already made, 

 than the age in which we live ; for there never was an age more distinguished 

 for ingenious research, for novel result and bold generalization. 



In the wonderful versatility of the human mind, the improvement, when 

 made, will very probably be made by paths where it is least expected. The 

 great inducement to Mr. Babbage to attempt the construction of an engine, 

 by which astronomical tables could be calculated and even printed by mecha- 

 nical means and with entire accuracy, was the errors in the requisite tables. 

 Nineteen such errors, in point of fact, were discovered in an edition of 

 Taylor's Logarithms printed in 1796; some of which might have led to the 

 most dangerous results in calculating a ship's place. These nineteen errors 

 (of which one only was an error of the press) were pointed out in the Nautical 

 Almanac for 1832. In one of these errata the seat of the error was stated to 

 be in cosine of 14 18' 3". Subsequent examination showed that there was 

 an error of one second in this correction, and accordingly hi the Nautical 

 Almanac of the next year, a new correction was necessary. But in making 

 the new correction of one second, a new error was committed of ten degrees. 

 Instead of cosine 14 18' 2" the correction was printed cosine 4 18' 2", 

 making it still necessary, in some future edition of the Nautical Almanac, to 

 insert an erratum in an erratum of the errata in Taylor's Logarithms. (Edin- 

 burgh Review, Vol. LIX. 282.) 



In the hope of obviating the possibility of such errors, Mr. Babbage pro- 

 jected his calculating, or, as he prefers to call it, his difference machine. 

 Although tliis extraordinary undertaking has been arrested, in consequence 

 of the enormous expense attending its execution, enough has been achieved 

 to show the mechanical possibility of constructing an engine of this kind, and 

 even one of far higher powers, of which Mr. Babbage has matured the con- 

 ception, devised the notation, and executed the drawings themselves an 

 imperishable monument of the genius of the author. Address at the Dedication 

 of the Dudley Observatory, by Edward Everett. 



LAYING THE GUNS OF A BATTERY WITHOUT EXPOSING THE MEN. 



Mr. Babbage has published the following method of laying the guns of a 

 battery without exposing the men to the fire of the enemy : 



The numerous casualties, chiefly by rule shot, which have occurred to those 

 employed in pointing guns at the object of attack, and also in examining their 

 effect after their discharge, induced me to recur to means which had pre- 

 viously been devised for reconnoitring with security. The highest skill is 

 required in the man who points the gun; his safety is, therefore, to be con- 

 sidered first. 



In pointing a gun at the object to be hit, the two sights of the gun and the 

 distant object must be brought into the same line. To do this, a man stands 

 behind the gun and looks along that line. But if, instead of a man in that 

 position, we put a good common looking-glass inclined at an angle with the 

 line of direction, the coincidence of the two sights and the distant object can 

 then be made by an observer placed in other positions. 



Suppose an officer is placed in the comer of a battery where neither rifle nor 



