HEFFER’S PUBLICATIONS. 
NOW RHADY. 
NOTES ON GEOLOGICAL MAP READING. 
By ALFRED HARKER, LL.D., F.R.S., F.G.S., Fellow of St. John’s 
College, Cambridge, and Reader in Petrology in the University of Cambridge. 
Demy 8vo, with 40 illustrations. Sewed. 3s. 6d. net. (Postage 4d.) 
The object of these notes is to teach the student to visualize a geological 
map as in three dimensions, and to show him that the questions which 
present themselves to the field-geologist reduce to exercises in very elementary 
geometry. This simplicity is gained by reckoning all slopes and dips as 
eradients, which enables one to dispense alike with trigonometry and with the 
protractor. The amount of dip, the thickness of a formation, the throw of 
a fault, etc., are thus measured directly upon a contoured geological map by 
the use of the scale alone. 
“Contoured geological maps are an aid to precision, and in this book they are 
reduced to the simplest terms by the device of reckoning slopes and dips as gradients, 
thus referring all questions to the scale without the use of the protractor of 
trigonometrical calculations.’—'he Times. 
SCIENTIFIC BOOKS AND PERIODICALS. 
Messrs. W. Heffer & Sons, Ltd., Booksellers, Cambridge, will be glad to 
receive offers of secondhand books and journals, for which they are prepared 
to offer full market price and pay cash. Particularly complete sets or long 
runs of the following :— 
ECONOMIST GEOLOGIST. 
GEOLOGISTS’ ASSOCIATION PROCEEDINGS. 
GEOLOGICAL MAGAZINE. 
GEOLOGICAL SOCIETY JOURNAL. 
MINERALOGICAL MAGAZINE. 
PALZONTOGRAPHICAL SOCIETY PUBLICATIONS. 
They will also be glad to have inquiries for both new and secondhand books, 
of which they carry an immense stock. Catalogues issued. 
LICENSED VALUERS FOR PROBATE. 
Telegrams and Cables: “ Heffer, Cambridge.”’ Telephone : 862 (2 lines). 
AN INTERESTING BOOK AT A REDUCED PRICE. 
THE NATURE AND ORIGIN OF FIORDS. 
By J. W. GREGORY, D.Sc., F.R.S. An excellent account of a pheno- 
menon which possesses immense interest to geologists and others. With 
diagrams and 84 very mteresting illustrations. 8vo, cloth. (Published 
John Murray, 21s. net.) In new condition, 8s. 6d. net. (Postage 1s.) 
_. . But we must conclude, and do this by expressing our hearty thanks to him 
for this admirable history of fiords and other forms of inlets of the sea. It will be 
a great boon to students, for it is a veritable encyclopedia, full of important facts, 
the collection of which must have entailed long and patient labour, because they are 
scattered about many publications in sundry languages and often not readily 
accessible.”’—F.G. Bonny, in Nature. 
“Prof. Gregory’s book should attract numerous readers outside the circle of 
professed geographers and geologists, and in so doing will guide them through 
scenes of grandeur and beauty to some glimpses of those deep underlying principles 
which control each tremor and pulsation of this restless world.”’—Twmes Literary 
Supplement. 
Cambridge : W. HEFFER & SONS, Ltd. 
