be prepared to find that the older moraines, in the path of the descent of the more recent glacier, would partly be dispersed, while some of its contents might be picked up, and eventually form part of the latter moraines of such districts Thus, in respect of undoubted ice striated blocks, we must in some cases be prepared to find them as not indicating with certainty the mode of origin of the deposit in which they are now found; but, like certain fossiliferous rocks, they may have been derived from an older formation.

An enthusiast is also apt to attribute all lake basins as due to the action of glaciers, and is tempted to confound the debris of rocks adjacent to steep slopes of mountain due to gravitation, with superficially similar remains left in such a situation (lateral moraines) by the retreat of an ancient glacier. Of course, a typical geological sceptic may, from prejudice, err as widely in the opposite direction, and remain stubbornly unconvinced in the face of the most conclusive evidence. But, in the latter case, although the individual may injure himself, his very stubbornness may benefit geological science in causing search to be made for still more perfect evidence, and in causing the evidences already in our possession to be submitted to still more careful sifting and weighing. I have been led to make these remarks, certainly not as a reflection upon the judgment or conclusions drawn by any of the very able observers commented upon in this review, but rather as my humble apology for venturing to criticise, generally, the opinions of men of better general qualification than myself, in respect of doubtful matters where independent judgment may, without either humiliation or presumption, arrive at very different interpretations with respect to the same facts. These remarks, moreover, apply as strongly to myself in respect of the contributions, for which I am responsible, regarding the evidences in favour of glaciation in Tasmania at two widely separated periods in the history of our rocks.

EVIDENCE OF RECENT GLACIAL ACTION IN TASMANIA.

Mr. Charles Gould, formerly the Government Geologist of Tasmania, was the first person who appears to have drawn attention to the abundant evidence of glacial action in the alpine valleys of Western Tasmania. His geological observations in these regions about 40 years ago, amid great hardships and privations, extended over a period long enough to enable him to work up the topography and to map the characteristic rocks of a very large portion of what has been, until recently, a comparatively unknown and almost inaccessible region. He has left no special memoir on the evidences of glaciation, but it was through verbal communica

tion to a personal friend of my own,* and one of his early associates, that I first, about 20 years ago, became aware of his discovery of many evidences of glaciation in Tasmania, especially in the valleys of the western highlands, which trend westward from the great elevated plateau of 4,000 to 5,000 feet level, which occupies an area of some 400 square miles in the centre of our heart-shaped island. On its northern and western sides this elevated plateau rests upon a less elevated but still more extended plateau, whose undulations preserve a general level of from 2,000 to 3,000 feet above the sea. The extreme western and southern part of the island presents a wild and broken array of lofty mountain ranges and isolated peaks, with deeply cut ravines and valleys, but whose bases rest generally upon lower levels than the western portion of the massive central plateau. Although Tasmania does not possess any mountains of great altitude, its mountainous character may be best realised when we consider that within its limited extent (26,215 square miles) there are 20 names of mountains over 4,000 feet in height, and as many as 50 named mountains whose heights exceed 2,500 feet.

The large inland plateau which maintains a general altitude of about 4,000 feet, rising at times to over 5,000 feet, is worthy of special attention when regarding the conditions necessary for the development of a sufficiently large permanent snowfield, which would suffice to feed glaciers flowing from its marginal slopes, during a period of extremely low temperature; for great height or extremely low temperature, per se, does not constitute all the necessary conditions for the development of glaciers.

We must also conjoin with either of these conditions breadth of area of the névé or snow catchment, and a great local precipitation of water vapour. The necessary combinations of these requisite conditions are not dreamt of by many who too readily invoke glacial action within the Tertiary or Pleistocene period in regions where it is difficult to realise the full combination of the essential conditions necessary for its production.

The following description, already given by me in a former publication,+ may help to afford the necessary information to those who may wish to know whether, in the event of a greatly lowered temperature, due to astronomical or other causes, the great inland plateau of Tasmania possesses all the other requisite conditions for the generation of glaciers: "The great central greenstone plateau of the Lake Country

:

* The Hon. Jas. Reid Scott, formerly Chief Secretary of Tasmania. Geology of Tasmania, p. 101.

(42° South lat.*), in its northern part especially, preserves a general rugged or undulating level of about 4,000 feet altitude, and its higher bosses and peaks and its valleys do not vary much more than 1,000 feet above or below this uniform level. From the Picton to Gad's Hill, a distance northerly of over a hundred miles, its westerly limit may be roughly traced, forming a bold and widely undulating margin relative to the western country, whose immediate general upland surface ranges between 2,000 and 3,000 feet above sea level. This margin is markedly broken by the elevated outlying spur forming the Eldon Range, near Lake St. Clair. From Gad's Hill in a south easterly direction to the Table Mountain; a distance of not less than 90 miles, its similarly indented margin presents a still bolder character as it approaches and contrasts with the lower fertile plains and valleys of the Meander and South Esk, which seldom exceed an altitude of from 600 to 700 feet above sea level.

"At the great northern and southern water divide, in the neighbourhood of the Table Mountain, it suddenly recedes and contracts, forming a large bight in the direction of the Upper Derwent tributares, notably the rivers Nive and Ouse, from which its level tends to fall, and its marginal boundaries, though frequently rising into high mountain. ridges towards Mount Wellington, no longer maintains the uniform boldness of outline which characterises its northern aspect. Nearly everywhere along and against this plateau and the greenstone crests of Mount Dromedary, Mount Nicholas, Eldon Range, Mount Gell, Grass Tree Hill, Constitution Hill, and most of the elevated south-eastern dividing ranges, the various members of the Carboniferous (Permo-Carboniferous) and Mesozoic rocks are seen to repose invariably in a horizontal position, or, at most, with a very slight dip towards or away from them."

From this description it will be apparent that, given a period of extremely low temperature, the great elevated plateau of Tasmania possesses, in a special manner, a great width of space at a high level for the formation of an extensive snowfield. It is also significant that in its present western margin, in the vicinity of the mountain valleys, where evidences of former glacial action are so abundantly manifest, there is now even the greatest amount of rainfall. This is shown by the records at the stations at Corinna, Strahan, and Waratah, on the western aspect, as contrasted with the records of Great Lake, Ross, Oatlands, and Bothwell, towards its eastern limits, as in the following table:

*A height of 5,000 feet in this latitude would have an inland temperature of that of nearly 6,500 feet altitude in the region of the Australian Alps.

So far as we can judge from existing meteorological conditions, which show that precipitation on the western portion of the plateau is nearly three times the amount of that in its eastern portion, it is obvious that if astronomical causes produced a lowered temperature in the Southern Hemisphere during the last period of maximum eccentricity, combined with winter in aphelion, the greatest precipitation of snow would take place near to the western margin of our great mountain plateau, and would there, probably, collect in sufficient mass to outweigh the short, hot summer melting, and to supply its western alpine valleys with numerous ice streams or glaciers; and while, therefore, supplying prima facie evidence of favourable conditions for the development of glaciers on the west, it is also suggestive as an explanation of the apparent total absence of evidence of glaciation on its eastern slopes, where the summer melting might exceed the amount of precipitation. any case, it adds greater force to conclusions drawn from the positive evidences of glaciation observed by various persons in the alpine valleys of our western highlands, a brief account of which may now be given in chronological order.

In

EVIDENCES OF GLACIATION IN THE ALPINE VALLEYS OF WESTERN HIGHLANDS OF TASMANIA.

I have already alluded to Mr. Charles Gould's observations, made about 40 years ago, of abundant evidence of the usual dynamic effects of ancient glaciers in the principal alpine valleys of the western highlands of Tasmania, although it is to be regretted that this most accomplished observer, so

far as I know, has left no special memoir of his extended observations on this subject.

In the year 1874, in company with the late Honorable J. A. Scott, W. C. Piguenit, Lieut. Burgess, and two other persons, I spent six weeks (all of the party laden with knap-. sacks weighing from 60 to 70 lbs.) in exploring the whole of the south-western region of the western highlands lying between the mouth of the Huon and Macquarie Harbour, and in making collections and observations on the geology and botany of this region. In the year 1879 I formed one of a similar party in exploring the northern region of the western highlands, including Gad's Hill, Middlesex Plains, Vale of Belvoir, Valentine's Peak, Mount Bischoff, head waters of the Mackintosh Valley, and other tributaries of the Pieman and Arthur.

In the year 1887, in company with my friend, the late C. P. Sprent, Deputy Surveyor-General, and five others, I traversed, on foot, and examined the whole of the region lying near to the route across the island by way of the Ouse, Bronte, Lake St. Clair, Mount King William I., Mount Arrowsmith, Collingwood Valley, King River, Mount Lyell, Queen River, Macquarie Harbour, thence northward across the Hentys, Mounty Heemskirk, Corinna, Whyte and Hazlewood Rivers, Magnet Range, and Mount Bischoff, to Emu Bay on the North-West Coast. I had the opportunity at this time to visit many of the lakes, including Lake Dixon, and to spend three days in examining more particularly the rock formations on Mounts Owen, Lyell, and Sedgwick.

I had thus ample opportunities for observing the many evidences of former glaciation in these regions, enabling me to confirm the earlier observations of Mr. Gould, and also enabling me to record the general results of such observations in my work on the "Geology of Tasmania," begun in the year 1884, and published in the year 1888. I only gave my general conclusions in this work, although my notes contained particulars regarding the abundant occurrence of moraines, roches-moutonneés, scooped tarns and lakes innumerable, huge ice-born erratics, polished rock surfaces, etc., in many localities; notably in the Gorge descending from Scott's Peak in the centre of the lofty and picturesque Arthur Ranges, and along the Alpha and other tributaries of the Craycroft and Huon River; in deep gorges descending from Mount Wedge towards Lake Pedder and the Serpentine; on the neighbouring slopes of the Frankland Range; in deep upper gorges and valleys of the tributaries of the Mackintosh River leading from Granite Tor and Barn Bluff; but particularly in the romantic valley of the Lakes Dixon and Undine, at the source of the Franklin, in the immediate