324 IOWA STUDIES IN NATURAL HISTORY 
to tens of thousands; even Ross, ten miles away and now an 
obscure village of a few hundred people, had a population of 
over ten thousand. Little by little the available gravels were 
washed out, the population dwindled, and the shacks crumbled. 
Hundreds of acres formerly covered with magnificent forests 
were left strewn with unsightly heaps and ridges of worked- 
over gravels. Even the famous placer, Mount d’Oro, is desolate 
in the extreme. However, much of the gravel was too coarse 
for the equipment of the gold-seekers to handle, and they only 
scratched the surface. In addition, this great gravel bed of 
fluvial, fluvio-glacial, and marine origin is at least fifty feet 
thick back of Hokitika. Any opening made into it immediately 
fills with water since its surface is but a few feet above sea 
level a condition with which the pioneer gold digger could not 
cope. After several failures at handling this coarse, heterogene- 
ous deposit it remained for the Rimu Gold Dredging Company 
to solve the problem. The company is a New York concern 
whose local manager, Mr. Cranston, received us most kindly and 
showed us the entire plant. The dredge is a floating dredge of 
the Brusies type and cuts a trench fifty-one feet deep to solid 
rock and two hundred feet wide. Forty feet of the gravel is 
under water. The floating part of the dredge is 116 feet long; 
the bucket line has 73 buckets, each carrying about ten cubic 
feet when full. Its capacity runs into hundreds of cubic yards 
per hour. The dredge is held in place by two struts which 
serve as anchors. When necessary to move forward, one strut 
is lifted and the outfit ‘‘walks’’ ahead. The stacker is 125 feet 
long. There are three decks for washing, and the mereury pro- 
cess is used for recovery. The gold is in the form of very tiny 
flakes, the occurenee being known as beach lead. The dredge 
handles boulders up to two or three tons with ease. The 350 
horse power used is hydroelectric and is developed at the Lake 
Kanieri power plant some ten miles away. Work goes on day 
and night and the recovery is ‘‘highly satisfactory’’. One 
eleven-day period netted 1105 ounces. The company owns 
twelve hundred acres, and at the rate of dredging for their 
first nine months it will take them thirty-five years to work out 
the claim. Mr. Cranston returned to America with us on the 
Tahiti. A new dredge with double the capacity of the first is 
in contemplation, and there are thousands upon thousands of 
acres of gravels untouched except for the surface washing al- 
