170 REPORT— 1870. 



and clothe themselves in dresses made of the bark of trees, The present inhabi- 

 tants of Kharkhand are Mohammedans. 



On tJie Physical Geography of Colorado and adjacent Regions. 

 By Governor GiLriN. 



On Lines for a Ship-Canal across iJie American Isthmus. 

 By General W. Hbine, U.S.A. 



The author visited the Atlantic side of the isthmus eai'ly in the present year on 

 a mission intended to examine the correctness of the statements of M. Lacharme, 

 an engineer who explored the interval from the Tuyra River on the Pacific side 

 and the Cacarica branch of tlie Atrato on the Atlantic, and declared there were no 

 great obstacles to the construction of a canal at that point, the length to be cut 

 being only 52 miles, .and the greatest elevation only 186 feet. The author was not 

 able to ascend the Atrato, but all he saw went to confirm M. Lacharme's statements. 

 These he gave in detail, showing that they were foimded on a conscientious survey, 

 with all necessary scientific instruments. From his own observations and those of 

 the recent United States Survey, the author demonstrated the utter impractica- 

 bility of any other part of the isthmus for the purposes of an interoceanic canal, 

 and insisted upon the necessity of a further sui'vey by the line of the Atrato and 

 Cacarica. 



On the Great Currents of the Atmosphere. 

 By John K. Laughton, M.A., F.E.A.S., F.R.O.S. 



The author pointed out several geographical facts which were opposed to the 

 received theory of the trade-winds, known as Hadley's theor3^ Heat does not 

 cause a wind towards any of the principal areas of greatest temperature ; either 

 towards the Desert of Sahara, the Arabian Desert, the interior of Australia, the 

 Red Sea, the Persian Gulf, or even, when carefully traced, towards the Great 

 Prairie of North America. The effect attributed to the rotation of the earth also 

 is not consistent with numerous observed facts, such as the S.E. wind in the Gulf 

 of Mexico, the N.W. wind on the coast of North Africa, between Cape Verde and 

 Cape Palmas, the N.W. gales in the North Atlantic, the S.W. wind on the south 

 coast of Australia, and A'ery many others ; the idea, indeed, appeared to have been 

 formed in a temporary forgetfuluess of the power of friction, which in the case 

 of air is very intense. Winds which, in accordance with Pladley's theory, have 

 been very generally divided into polar and equatorial, seem more naturally to divide 

 themselves into easterly and westerly. As our experience grows larger, we learn 

 that the westerly winds have an extent and a power incompatible with the idea of 

 their secondary nature. They extend from 60° N. to 60° S., interrupted only by 

 the trade-winds. The trade-winds are small in comparison, and of very limited 

 height, the westerly winds blowing above them as strongly as they do both above 

 and near the sm-face in temperate zones. The westerly are really the primary 

 winds, whilst the equable trade-winds, of very limited volume, are reflex streams 

 of air caused by the impact of the great westerly winds on the continental barriers, 

 whether against mountain-ranges or against the more sluggish air which lies over 

 the land. In the Atlantic we see the main westerly stream of air dividing, on 

 about the parallel of 45° N., and turning north as a S.W. wind on our coasts, or 

 south as a N.W. and N. wind on the coast of Portugal. On the other hand, at the 

 extreme west," the westerly wind continually dragging away the air fi'om the eastern 

 side of the Rocky Mountains, causes such a tendency towards a vacuum, that the 

 air from the south and north is induced towards it. It was impossible to say 

 definitely why the atmosphere should have this prevailing westerly motion, but the 

 author was inclined to seek its cause in the attraction of the heavenly bodies. 



