];j4 Robert A. Keble : 



Hass Strait. The soutl.ern frin^'o is found at various localities; 

 on the north eoast of Tasmania, its eastern fringe is probably in 

 the vieinity of tlie partly submer<>:ed range between Wilson's 

 Pri.iiK.ntory and tlie nortli-east eoast of Tasmania, and its extension 

 westward is pr()l)U'matiical. 



As a mncssarv i)remise to the evolution of erosional forms on 

 tlie mainland, it is assumed that Harker'si assertion relating tO' 

 gradient, applied to the Bass Strait lava field. According to 

 Barker, the suiface of a lava stream has a certain inclination 

 depending mainly on its viscosity and rapidity of cooling, but the- 

 actual gradient is very slitzht in the case of a stream of large 

 volume. He cpiotes Avell-known examples from different parts of 

 the world. 



The eruption of Laki, on the south-west coast of Iceland, is 

 an example within histoi-ic times, for in 1783 an old fissure re- 

 opened for twenty miles and streams of basalt welled out from a 

 number of new cones. The confluent lava streams formed floods 

 which flowed over the surrounding country, and down two valleys' 

 — in one of which it ti-avelled fifty miles, and was in places from 

 twelve to fifteen miles in l)readth, and eight hundred feet deep. 

 The present volcanic activity of Iceland dates from the Eocene, and' 

 is supposed to be connected Avith the lava field of Antrim, Avhich 

 extended far within the Arctic circle. In Iceland it exceeds a 

 thickness of 5000 feet. 



The Columbia lavas of the United States are from two hundred 

 to two hundred and fifty thousand square miles in extent, and 

 have a maximum thickness of four tho-usand feet. The lava fields 

 of the Deccan, Hawaii, Colorado and other areas* may also be cited. 

 An area in which the lava is in many respects in a similar stage 

 of erosion to the Older and Newer Basalt lava residuals of Vic- 

 toria is that the Tinkaret, desci'ibed by Dutton^ in his Mono- 

 graph of tlie Grand Canyon district. 



The Older basalts of Victoria^ are assumed to have issued from 

 eruptions mainly of the fissure type. Dykes and pipes have been 

 found in various parts of the area by Messrs. Ferguson," Chap- 

 man and Teale,'^ Ower, and others. It matters little to the general' 



1 Vide Biblioj; , No. 6. 



2 Vide Riblio};., No. 2. 



3 Prof. Skeats fommeiited on the Tertiary basalts in his Presidential Address to the Brisbane- 

 JleetiMif of the Australasian Association for the Advancement of Science for 19u9. Bibliojf., No. 20.. 



4 Bibliotf., No. 3. 



5 Ibid.. No. 1. 



6 Ibid., No. 18. 



