170 ANNUAL OF SCIENTIFIC DISCOVERT. 



The experience of Mr. Briggs was of a similar character. He con- 

 sidered that many cast-iron cylinders were cast too thick, under the 

 supposition that they were strong in proportion to their thickness. 

 There is a limit to the strength of all cast-iron cylinders, as it relates 

 to their thickness, and efforts should be made to obtain thinner cast- 

 ings, as they were more uniform in strength, more dense, and better 

 calculated to sustain pressure. 



The general conclusions arrived at by Mr. Briggs were as follows: 

 Three tons per circular inch he considered to be the bursting pressure 

 of press cylinders. The maximum thickness of metal, when all due 

 care had been exercised in its composition, should not be more than 

 the radius of the bore of the cylinder. Two tons per circular inch 

 was a safe pressure to work up to, and this he should pronounce to be 

 his own standard. 



LUNAR TIDES ON THE AMERICAN LAKES. 



ERRATA. 



We have received from Col. Graham, U. S. A., the following 1 errata, in the paper 

 entitled " Existence of a Lunar Tidal Wave on the great American Lakes," com- 

 municated by him to the Annual of Scientific Discovery for 1861, pp. 167-171 : 



Page 169. In Table 1, opposite 1 hour 30 minutes before the moon's meridian 

 passage, the " elevation of the lake surface in decimals of a foot," given in the 

 second column, should be 0.098, in lieu of 0.089. This ordiuate is derived from 

 12(53.773 divided by 340, which gives 3.71697, or, for the nearest decimals of three 

 places, 3.717, from which we deduct 3.619, and get the ordinate, 0.098. 



Page 170, 16th line from top, for " six semi-diurnal tides," read " three semi- 

 diurnal tides." 



Page 171, 9th and 10th lines from the top, for " equal to 3.408 inches," read 

 " equal to 3.048 inches." Same page, 12th and 13th lines from top, for " the estab- 

 lished mean for the port of Chicago," read " the Establishment for the port of Chi- 

 cago." 



