1852.] 



BIGSBY GEOLOGY OF THE LAKE OF THE WOODS. 



401 



irregular, is best learnt from a glance at the accompanying Map, 

 PI. XXII. 



It is divided into three parts (each having its own name) by a 

 promontory, 40 miles in direct length, which, beginning at the south- 

 eastern angle of the lake, extends N.W., and approaches vsdthin half 

 a mile of the western shore 30 miles from the northern extremity of 

 the lake. 



This promontory first separates Whitefish Lake, and then Lake 

 Kaminitic, or the Lake of the Woods proper, from the Lake of the 

 Sand Hills, the entrances to each being barred by islands. 



Whitefish Lake has never been properly examined. I have seen it 

 from three points 25 miles apart, and noticed several lofty basaltic 

 islands. It is supposed to be 120 miles round. 



The south and south-west side of Sandhill Lake has few or no 

 islands, and its shores sweep around in large uniform curvatures 

 faced by sand-hills or gravelly banks, which sink behind into rice- 

 marshes or wide-spreading lagoons. Westward the land rises very 

 slowly, until at 70 or 80 miles from the lake it becomes a grassy 

 plain ; and wet savannahs, with clumps of fine trees here and there, 

 prevail largely about Monument Bay. The greenstone clifPs and 

 high pine-covered islands of the Kaminitic render this part of the 

 lake extremely picturesque. 



Although, from the marshy, woody, or shattered state of the coun- 

 try, its rocks can only be examined at intervals, still their nature and 

 disposition are easily recognised, especially when we notice the di- 

 rections and dips of the metamorphic rocks on a good map. These 

 are in two groups, one on each side of a mass of granite, and dip 

 respectively northerly and southerly from it at a high angle (see 

 fig. 1). This granite, which I consider to be the axis of an anti- 



Fig. 1. — Diagram of a secfAon across the Lake of the Woods, passing 

 near Pipestone Island, Lake Kaminitic. 



N.N.W. S.S.E. 



a. Granite. 



b. Syenitic greenstone. 



c. Chloritic greenstone. 

 c'. Porphyritic greenstone, 

 c". Greenstone conglomerate 



clinal ridge, comes from the west main in and to the north of Monu- 

 ment Bay, crosses, with an E.S.E. trend, the centre of the lake, 

 chiefly (so far as swamps and other local hindrances allow us to see) 

 along the south shore of the great promontory, occupies most of the 

 adjacent islands in Sandhill Lake, together with much of its S.E. 



