264 



Miles and a,nd begins a traverse of the northwestern Hmb 

 of the anticHne. In a distance of about 2 miles 

 (3-2 km.) from the summit, the railway again 

 enters the encircling area of the Limestone 

 series and shortly approaches the shores of 

 the Northwest Arm of Sydney harbour around 

 the head of which the railway passes. The 

 low valley at the head of the Northwest Arm 

 is floored by strata of the Limestone series 

 dipping to the northwest at angles of from 

 15° to 25°. 



10-4 m. Leitch Creek Station — Alt. 10 ft.( 3 m.). 



16-7 km. A short distance beyond Leitch Creek station, 

 at the crossing of Leitch creek, a view up the 

 valley shows the ridge of the Boisdale hills 

 rising to altitudes of 600 to 800 feet (180 to 

 249 m.). The Boisdale hills are composed of 

 Pre-Cambrian rocks and form the western 

 boundary of the Carboniferous basin. The 

 Carboniferous Limestone measures extend up 

 the valley of Leitch creek and there repose 

 directly on the Pre-Cambrian rocks without 

 any intervening strata of the Conglomerate 

 series. 



A short distance beyond the crossing of 

 Leitch creek, the railway passes through cuttings 

 in reddish shales and sandstones possibly 

 belonging to the Point Edward formation 

 which in places lies between the Limestone 

 series and the Millstone Grit. Just beyond 

 this point, where the railway skirts the shores 

 of a small lake, the area of Millstone Grit 

 strata forming the summit of the western 

 limb of the anticline, is entered upon. Small 

 cuttings in Millstone Grit strata occur along 

 the railway. The measures dip to the north- 

 west at angles of 10° to 20°. The Millstone 

 Grit strata form a ridge exending in a northeast- 

 southwest direction and in which the strata are 

 arranged in a shallow syncline. To the south- 

 west, the Millstone Grit strata are encircled 

 by measures of the Limestone series which 

 rest on the Pre-Cambrian rocks of the Boisdale 

 hills. To the northwest, the Millstone Grit 



