228 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1957 



Lt. John E. Pillsbury, who became a Rear Admiral after distin- 

 guished service in the Spanish War, spent many years in the Survey, 

 advancing the techniques of deep-sea exploration and inventing a 

 direction-indicating current meter of great value. Surface current 

 observations carried out by tracking marked bottles led to the in- 

 tensive study of the Gulf Stream in 1848 and since. 



Among the many outstanding later developments in oceanographic 

 instrumentation were those of Comdr. C. D. Sigsbee, later a Rear 

 Admiral, whose name is immortal for his contributions to deep-sea 

 exploration. He commanded the Blake in the Gulf of Mexico in 

 1875-77, where he adapted Sir William Thomson's sounding machine 

 to deep work, in part by the addition of a registering sheave to indi- 

 cate the length of wire paid out. He also invented a water cup to 

 bring up samples from several depths at one haul, and a collection 

 trap for biological samples. In addition to these effective means of 

 perpetuating his memory, he later commanded the Maine when she 

 was lost at Havana. 



In the early twentieth century, Nicholas Heck and others developed 

 the wire drag, following the wrecking of the cruiser Brooklyn on a 

 pinnacle rock at New Bedford. This method, an improvement on 

 earlier clumsy pipe sweeping devices, has been widely used to sweep 

 the passages of rocky coasts to disclose hidden dangers, such as the 

 famous "Washington Monument Rock" which rises to within a few 

 feet of the surface from general depths of 650 feet in southeast 

 Alaska. 



A relatively recent development is the fathometer, brought into 

 useful form by the Submarine Signal Company with the help of the 

 Survey. Its value is beyond reckoning. Another was the radio- 

 acoustic ranging system, used for many years as a distance-measure- 

 ment device until superseded by electronic position-finding methods. 

 Radio-acoustic ranging used the transmission times of underwater 

 sound signals. In the course of development work in this field, 

 Comdr. O. W. Swainson and Dr. Karl Dyk, working off the Cali- 

 fornia coast on the Pioneer in the early 1930's, discovered and ex- 

 plained a striking phenomenon, earlier predicted by A. L. Shalowitz, 

 which later led to the operational use of SOFAR, a signaling device. 

 Sound signals travel great distances when directed into certain mini- 

 mum-velocity layers, constituting effective sound-conducting channels. 

 Vast areas of offshore hydrography, controlled by the radio-acoustic 

 ranging method, have benefited by this fortunate circumstance. 



Charts in Hassler's time were laboriously prepared by engraving 

 myriads of details on stone or copper plates, from which impres- 

 sions were made by hand. The first one of all, showing Newark Bay, 

 was printed from the stone, which gave poorer definition than copper. 

 In 1844 the first copper-plate engraving, of New York Harbor, was 





