208 Forestry Quarterly. 



A very exhaustive discussion of the known 

 Migration and also of the unknown elements under 



of Birds. controversy in the annual migration of birds 



by Dr, F. Knauer, makes interesting read- 

 ing through four numbers of the Centralblatt. 



Der Vogelzug und seine Ratsel. Centralblatt fiir das gesammte 

 Forstwesen. April, May, June, August, 1906, pp. 212-217, 26 1- 

 265. 



ROADS AND SURVEY. 



The Swiss journal reprints in full with il- 

 Transportation lustrations the chapter from Meister's well- 

 by known work on the city forest of Ziirich 



Slides. which deals with the use of log slides of 



varying construction, specially developed 

 in that forest. There are three types in use, the wire rope (over- 

 head) slide, the wooden slide, and the wire rope road, a combination 

 of the two. The earth slide is excluded, because steep slopes and 

 horizontal terraces alternate. 



The wire rope slide, with a carriage moving on the rope, is one 

 of the most effective means of transportation in the Alps for the 

 highest and least accessible points, capable of transporting small 

 and large amounts across coves and valleys through the air. It re- 

 quires yarding at the top and at the base and means of tightening 

 and of braking the rope. It is applicable mainly for log transpor- 

 tation, working without regard to weather conditions and without 

 damage to the logs. Its disadvantage is the necessity of working 

 from a terminal yard and not along its line. It is also difficult and 

 expensive to re-locate, hence is to be used mainly where permanent 

 transport from a collecting point is intended. 



The wooden slide, built of logs (see Forestry Quarterly, Vol. 

 Ill, No. 2), is more generally serviceable than the former. It de- 

 pends, as does the former, on proper grade, which, for the upper 

 third, was found to require at least 1 5 degrees, if the two-thirds are 

 to be run with less than 15 degrees. This consideration determines 

 the possible length of the slide. The conditions in the Sihlwald ter- 

 races, with a maximum grade of 5 degrees, exclude long slides, 

 which are otherwise desirable, the longest being less than 1,000 

 feet. They are either permanent or movable. The former, which 

 used to be constructed of round poles, 5 to 8 meters long, with 12 to 



