16 



tacked by the shipworm known as the teredo navalis" — again with no mention made 

 of Limnoria. 



Evidence that this borer was observed shortly after 1869 is given by the state- 

 ment of Mr. T. J. Arnold, Engineer of the Board, in 1873: "The limnoria terebrans 

 has only recently- made its appearance in our waters." It therefore appears that the 

 three principal borers now present in the Bay became noticeably destructive at the 

 following approximate dates: Baukia, \ii50\ Limnoria, 1870; and Teredo, 1913. That 

 these were the dates of their arrival in the harbor cannot be established as more 

 than conjecture. Some of the species appear to be indigenous. 



Simultaneously with the beginning of wharf construction in 1849, work was 

 started on grading off the sandy hills of the mainland, the excavated material being 

 dumped into the Bay along the shore. In 1851 the State Legislature passed an act 

 defining the city bulkhead line as that formed by certain proposed streets which 

 approximated the desired limit. This caused a saw-toothed alignment in sections 



Fig. 6. San Francisco Bay about 1853; Goat Island in background. 



where it was necessary to follow around the rectangular street intersections to form 

 a general curve. The act also prescribed that wharves could only be built beyond 

 the w'aterfront line on extensions of the city streets and for a distance not to exceed 

 two hundred yards. This was the first definite ruling on harbor development to which 

 early structures were required to conform. The ruling was faulty, however, since the 

 streets were laid out only to the waterfront line; hence a wharf extension of any one 

 of them could go in any direction beyond it. This resulted in many interpretations 

 within the law, and many irregular wharves. The filling of the cove area progressed 

 so rapidly that by 1855 the wharves of 1850 were completely surrounded, and other 

 such structures were finding it difficult to keep in advance of the fill far enough to 

 provide adequate depth of water. This presented a new problem because of the lack 



