In the foregoing account it has been my aim and endeavour to describe the geological formations in which the caverns existed; this will be seen at a glance in the following table:—

Taking the two classes together as representing thirty distinct series of cavernous localities, one is found in the New Red Sandstone formation, two in the Carboniferous, two in the Devonian or Old Red, seven in the limestones of the Upper, two in those of the Middle, and six in those of the Lower Silurian formation, three in the Huronian rocks of Sir William Logan, and seven in the Laurentian rocks of the same geologist. In the last of these they are present in the interstratified bands of crystalline limestone, characteristic of this formation in Canada.