Editorial Comment. . 263 
this Avork. The historian comes at times in his researches to 
the edge of a gap where the connection is lost, the records are 
missing, the chain is broken. Fire, or some one of the num- 
erous accidents to which his materials are exposed, has de- 
stro3^ed them and left a chasm that can never be altogether 
filled. A few scattered extracts from the lost volumes, a few 
detached references to unrecorded events, a few isolated and 
disconnected letters and papers are all that he can obtain and 
from these he must to the best of his ability reconstruct so 
much of his missing fabric as will make the story which he is 
putting together intelligible. 
And the geologist is in a similar condition in essaying to 
reconstruct the past geography of the globe. His materials 
like those of the historian are hidden in places that are diffi- 
cult of access. They are being slowly brought to light by a 
multitude of isolated and independent workers from the 
stony records of the Earth . But in spite of all their labor for 
so many years past the gaps are still far more extensive than 
the chapters and many a link must be established before any 
connected story can be compiled out of the disjointed mater- 
ials. 
Few parts of the world have been more thoroughh' exam- 
ined than the British Isles. The labors of the Geological Sur- 
vey aided, backed and sometimes corrected by those of a host 
of equally able and zealous working geologists without official 
recognition have put on record a mass of facts the mastery 
and use of which require endless patience and persevering 
industry. The outcome of these is shown in the work before us 
— the latest and perhaps the most pretentious (using the 
word in no uncomplimentary sense) that has yet appeared. 
Previous and excellent attempts were made by professors 
Geikie and Hull and by the author, but none of these ven- 
tured so far in the direction of mapping the past continents 
and island, oceans and lakes as Mr. Jukes-Browne has done in 
the work before us. 
Yet he is fully conscious of the ditiiculty of his task and 
claims a due consideration from his reader for the errors and 
imperfections that are inevitable to a somewhat daring at- 
tempt especially in the earlier and more obscure chapters. He 
says : 
''The imperfection of our knowledge is one great difficulty 
