ANNUAL REPORT OF THE SUPERINTENDENT OF THE U.S. COAST SURVEY, 1651. 



[1853 



The decaying soft parts of all these animals undoubtedly have 

 their influence upon the chemical process, by which the limestone 

 particles of their solid frame are cemented together, in the forma- 

 tion of compact rocks. Upon this point wo may expect further 

 information from Professor Horsford, who is now submitting to 

 chemical analysis all the variety of rocks and the solid stems of 

 the different corals obtained in Florida. 



Respecting the relations of the solid and soft parts of the living 

 coral, and their mode of growth, we would refer to a paper of 

 ours now in press, to appear in the next volume of the Smith- 

 sonian Contributions to Knowledge. 



COKAL BEEFS. 



After examining a growing coral reef, so full of life, so fresh 

 in appearance, so free from heterogeneous materials, in which 

 the corals adhere so firmly to the ground, or if they rise near the 

 surface, seem to defy the violence of the ocean, standirig un- 

 injured amid the heaviest breakers, an observer cannot but won- 

 der why in the next reef, the summit of which begins to rise 

 above the level of the water, the scene is so completely changed. 

 Huge fragments of cora's, large stems, broken at their base, 

 gigantic boulders, like hemispheres of Porites and Macandrina, 

 lie scattered about in the greatest confusion ; flung pell mell 

 among the fragments of more delicate forms, and heaped upon 

 those vigorous madrepores which reach the surface of the sea. 



The question at once arises, how is it that even the stoutest 

 corals, resting with broad base upon the ground, and doubly se- 

 cure from their spreading proportions, become so easily a prey to 

 the action of the same sea which they met shortly before with 

 such effectual resistance ? The solution of this enigma is to be 

 found in the mode of growth of the corals themselves. Living 

 in communities, death begins first at the base or centre of the 

 group, while the surface or tips still continue to grow, so that it- 

 resembles a dying centennial tree, rotten at the heart, but still ap- 

 parently green and flourishing without, till the first heavy gale 

 of wind snaps the hollow trunk, and betrays its decay. Again, 

 innumerable boring animals establish themselves in the lifeless 

 stem, piercing holes in all directions into its interior like so many 

 augurs, dissolving its solid connexion with the ground, and even 

 penetrating far into the living portion of these compact commu- 

 nities. The number of'these boring animals is quite incredible, 

 and they belong to different families of the animal kingdom : 

 among the most active and powerful we would mention the date 

 fish, lithodomus, several saxicava, petrieola, area, and many worms, 

 of which the serpula is the largest and most destructive, inasmuch 

 as it extends constantly through the living part of the coral 

 stems, especially in macandrina. 



On the loose basis of a macandrina measuring less than two 

 feet in diameter, we have counted not less than fifty holes of the 

 date-fish^ — some large enough to admit a finger — besides hun- 

 dreds of small holes made by worms. 



But however efficient these boring animals may be in preparing 

 the coral stems for decay, there is yet another agent, perhaps still 

 more destructive. We allude to the minute boring-sponges 

 which penetrate them in all directions, until they appear at last 

 completely rotten throughout. * * * * * 



The experiments of the late Sears C. Walker* on the subject 



* At a meeting of the officers and members of the U. S. Coast Sur- 

 vey, the Superintendent, Professor A. D. Bache, delivered the following 

 sketch of Mr. Walker's scientific attainments : — 



We have met to pay our tribute of respect and feeling to one of our 

 most distinguished aud valued associates, Sears 0. Walker, Esq., 

 whose failing health for more than a year past has kept us in anxiety 

 and fear for the result which has now come. Mr. Walker was at- 

 tacked by bilious fever some weeks since ; and though his mind was 



of galvanic wave time, furnish very valuable information on the 

 propagation of the electric current. The results arrived at by 

 that distinguished astronomer are given below : — 



1. That the average of all our experiments to that time (1850) 

 indicates a velocity of propagation of the inducing waves of 

 15,400 miles per second in the iron wires of a telegraph line. 



2. That the velocity of propagation through the ground ap- 

 pears to be less than two-thirds of the velocity in the iron wires. 



These conclusions were in accordance with the independent 

 results of the researches of Dr. B. A. Gould and Mr. Karl Cul- 

 man, previously read, and since published in the proceedings of 

 the American Association for the Advancement of Science, at 

 their meeting in New Haven in August, 1850. 



There have been three independent series of observations for 

 the value of wave-time, made since October last, 1850. The 

 first experiment was repeated on several nights, between Seaton 

 Station and Portsmouth, Va. The distance on the iron wires is 

 268 miles, and the distance through the ground is 180 miles, 

 The clock station excess, in the electrotonic readings, by a mass 

 of 221 measures, was -J-0s.024, while the computed excess for 

 the assumed velocity of 15,400 miles per second, in the iron 

 wires, was +0s.035. The difference between theory and com- 

 putation is, theory greater by +0s.011. 



The second experiment was made from Charleston, S. O, to 

 Augusta, Ga., in the winter of 1851. The distance on the iron 

 wire from Columbia (where the Charleston end went to the 



clear, his physical strength was not adequate to resist the effects of 

 the disease. 



The services which Mr. Walker has rendered to the coast survey are 

 known in a general way to most of those whom I address. He had 

 made the largest collection of American observations of moon culmina- 

 tions and occupations ever made in the country, and prepared to dis- 

 cuss them thoroughly for longitudes, and to bring them to bear, as far 

 as applicable, by the geodetic results of the coast survey, upon the lon- 

 gitude of a central point. The magnitude of this labor w ould have 

 appalled an ordinary mind. He knew that by perseverance it could 

 be accomplished. During this discussion he reached the conclusion 

 that the longitudes from moon culminations could not be reconciled 

 with those from occupations, and that the theory must be re-examined 

 for an explanation. His published reports show the successive steps 

 of his investigation, which was not completed at the time of his de- 

 cease. In the midst of it, the new, attractive, and important subject 

 of determining differences of longitude by the telegraph was commit- 

 ted to him, and he threw all his zeal and knowledge into the solution, 

 of this problem, and brought it to the successful condition in which it 

 now is. He early saw the impossibility of reading a near result by 

 merely repeating the transmission and reception of signals, beats of a 

 clock or chronometer, and that the beats sent and received must be of 

 time-keepers regulated to different times — as, for example, mean solar 

 and sidereal, and seized all the consequences flowing from this princi- 

 ple. The telegraphing of transits of stars was original with him. 



He soon became satisfied of the necessity for graphic registry of the 

 time results, and invited the co-operation of Mr. Saxton, of Mr. Bond, 

 of Prof. Mitchell, and of Dr. Locke in the solution. With him origi- 

 nated the application of this method to the registry of time observa- 

 tions for general astronomical purposes, now developed by so many 

 ingenious modes, and known as the "American Method." His re- 

 searches on galvanic wave-time, growing out of these experiments for 

 difference of longitude, are by far the most valuable contributions yet 

 made to this branch of science. In this subject alone Mr, Walker ac« 

 complished a most remarkable five years' work ; but this was only a 

 part of what his mind found there to do, and, aside from this and 

 labors of daily and nightly routine in computing and observing, he 

 accomplished a work — investigation of the orbit and computation of 

 an ephemeris of Neptune — which of itself would have given him an 

 undying reputation. I cannot in this place describe how the training 

 of a life was obtained which led to these brilliant results for our work, 

 and for American science ; nor can I trust myself now in an analysis 

 of the mind and heart of this friend for many years. I have faintly 

 pencilled his doings while closely connected with our work, shadow- 

 ing merely his claims to our admiration, respect and gratitude. — 

 Republic, Feb. 8. 





