FLOATING AND RAFTING 429 
The safe towing periods are from June 15 to September 15 
and, under favorable conditions, the trip can be made in from 
eighteen to twenty days. 
A different type of ocean-going raft was developed some years 
ago in British Columbia which does not require the use of a cradle 
such as is used in building the Benson rafts.^ They are preferred 
for use where rafts are built in salt water because marine borers 
Fig. 157. — General Form of the Davis Patent Log Raft. 
attack cradle timbers and necessitate frequent and costly repairs. 
A bottom tier of logs is first formed by enclosing an area 70 
feet wide and 150 feet long with boom sticks which are bound 
together with cables. A swifter is also placed crosswise of the 
side boom sticks at each end in order to keep the raft rectangular 
in shape. A bottom tier of logs is then placed in position between 
the swifters and bound together with Ij-inch cables or with 
chains. 
Several tiers of logs are then placed on the floor and a chain 
passed around them and fastened to the outside boom sticks. A 
top load is then placed on the raft and bound together with cables 
1 See Fis. 157 
