120 The Ottawa Naturalist. [Jan. 



simple method of measuring the beds collected from is to cut 

 a light pole 10 or 15 feet in length and mark it with bands of 

 peeled bark at intervals of 5 feet, one of the 5 -foot subdivisions 

 being marked off into 1-foot spaces. The section can then be 

 measured by holding the pole at right angles to the bedding 

 and using it yard-stick fashion. In the case of horizontal beds 

 exposed along the slope of a hill or mountain-side, the aneroid 

 barometer or a Locke's hand level is generally used. When the 

 beds are inclined, neither of these instruments will suffice. The 

 method used by Blackwelder for measuring sections of inclined 

 strata is a modification of the Walcott method, and includes the 

 use of a clinometer compass attached to a rod 5 feet 1 inch in 

 length. Walcott describes this method as follows: — 



"The strata, in section to be measured, were inclined to 

 the east 40°. Placing the lower end of the rod at the base of 

 the section, I inclined the rod towards the edges of, and at a 

 right angle to, the line of the dip of the strata, which was in- 

 dicated by the needle of the clinometer standing at 40°. Then, 

 looking through the compass sights the point where the line of 

 sight touched the ground was marked as the next station for 

 the rod, and on this station the base of the rod was placed for 

 the second sight, which was made exactly as in the first instance, 

 and so on to the end of the section. Frequent trials were made, 

 at the exposed outcrops, to determine the angle of dip of the 

 strata, so that the rod might be held at a right angle to it." 



The application of this method is clearly shown by Black- 

 welder's figure which is given below. 



Fig. 1. Diagram illustrating the meaEurement of strata by means of a spirit level 

 clinometer and sighting arm attached to a five-foot rod. (After Blackwelder.) 



In case the collector is not provided with a clinometer 

 compass, fairly accurate measurement of a section of inclined 

 beds may be made with the aid of a roughly improvised T- 



