xii INTRODUCTION 



On the continent of Europe the first elevator or ladder dredge 

 was designed and patented by Savery in 1718. The first dredge of 

 this type in England in 1747. Three years later in France iron 

 buckets were first used on a ladder dredge. In 1781 a ladder dredge 

 was built in England and operated by horse power. 



The first steam dredge was built in England in the year 1796, 

 the engine being designed by the inventor James Watt. This was 

 followed in 1804 by a machine of the same design, only heavier. 



Little progress was made in dredge designs and building during 

 the first half of the 19th century. During this time there was built 

 in England a dredge of rather unusual design. A barge or scow had 

 two movable wings at the stern that reached if desired to the two 

 banks and to the bottom of the stream. At the back was a scraper 

 that loosened the dirt, and the two wings, with the aid of the current, 

 swept the loosened material ahead and finally deposited it at the 

 mouth of the stream. The wings formed a temporary dam, which 

 gave enough head to force the scow downstream. Some noteworthy 

 work was done with such dredges. 



The first hydraulic or suction dredge was suggested in France in 

 1867, which was really the beginning of the construction of modern 

 dredges. In 1872 the first dredge of this type was built in America. 

 Cutters were first placed on hydraulic dredges in 1878. The credit 

 of building the first hopper dredge in 1861 is given to England. 



The dipper type of dredge was not originated in America, but 

 it has been developed in the United States and is considered dis- 

 tinctly an American dredge. 



In the last few decades wonderful strides in these machines 

 have been made. From small buckets operating slowly, buckets 

 of more than 10 cu.yds. are used with a pull of about 100,000 Ibs. 

 being exerted on the dipper, and three or four dips made per minute. 

 Likewise the depth to which they will excavate has been greatly 

 increased. 



The grapple dredge has been an evolution of the dipper machine, 

 and as its distinguishing feature is the clamshell or orange-peel 

 bucket, it is evident that it is a modern machine. 



Since 1890 both in Europe and America wonderful advances 

 have been made in all types of dredges. One country has introduced 

 a design while another has developed it and improved upon it. 



This has been so regarding the ladder dredge for mining pur- 

 poses. In the sixties much experimental dredging for gold was 



