from the llall el's- Point Ex^^losion. 301 



certain railway maps and those of U.S. Coasts Snrvey. I 

 know not what anionnt of precision belongs to the Coasts Sur- 

 vey of New- York Harbour and the Hudson Ri^er. I readily 

 credit it with all the exactitude which characterizes the na- 

 tional scientific work of the United States ; but I cannot credit 

 any Coasts Survey designed for maritime commercial and social 

 purposes, extending, as in this case, over an extreme range of 

 several miles of coast, as assuring sufficient exactness to be 

 made the basis for the measurement of distance as an element 

 for determining any great physical problem. Nor do the in- 

 strumental arrangements for noting the time of arrival of the 

 several waves at the several stations seem to me wholly free 

 from objection. A more exacting critic than I am at all dis- 

 posed to be, must remark that, amongst the four different ob- 

 servers, no attempt seems to have been made to determine the 

 personal equation of any one of them ; the differences due to 

 the different observers Avould very differently perplex the 

 results w^here their respective ranges differed so much in length 

 as well as in other conditions, and where in each case three 

 senses (hearing, seeing, and nerve-transmission) were brought 

 into play. 



From all these circumstances, as v/ell as from others which 

 for brevity I omit to notice, I cannot regard the results ob- 

 tained by these operations as of authority ; and I feel justified 

 in protesting against their being viewed as any scientific check 

 or control, or as capable of revising the results obtained by 

 myself several years ago upon simpler and more ascertainable 

 data and by more exact methods, in part w^ith the assistance of 

 my eldest son, Dr. J. W. Mallet. As my son is intimately 

 acquainted with the conditions involved in seismologic inves- 

 tigation and wath the methods and precautions adopted by me, 

 I cannot but presume that he was not fully informed as to the 

 circumstances relating to this great explosion in New- York 

 Harbour when he suggested its subsidiary application to 

 seismic physics, which I learn he did from the first para- 

 graph in General Abbot's paper, by a communication addressed 

 to the Smithsonian Institute in June 1876. 



In these objections I wdsh to be clearly understood as 

 having no a priori difficulty in accepting a higher velocity of 

 wave-transit than the highest attained experimentpJly by my- 

 self. It is highly probable that such may be elicited by future 

 experiment. But should such cases arise, their results, like all 

 great physical truths, should only be credited upon unexcep- 

 tionable observations or experimental evidence. While feeling 

 justified in making these objections, I wish to disclaim all con- 

 troversial spirit or intention ; loss of sight, indeed, and dimi- 



