BY THE PORTILLO PASS, AND RETURN HOME. 67 



in my saddle-bags, intending to deposit it in tlie tanks at Colina. On our arrival I was aston- 

 islied to find that it was not only alive and hearty as ever, but eagerly bent on biting me. Of 

 course I dropped the reptile ; and it soon made its way to a large party of women, who had 

 collected at the posada to celebrate the new-year's day. The amoimt of squalling and fluttering 

 of petticoats that took place, and lasted till I got his snakeship by the throat, may be better 

 imagined than described. 



I have said that it is the universal impression in Mendoza that goitre is caused by the use of 

 the water of the river ; it is also a very common belief in Santiago that it is there produced by 

 the water of the Maypu. Indeed, many of the old inhabitants say it was not known before 

 that water was brought to the city by the Maypu canal. There is a peculiar feature about both 

 of these rivers which appears to justify this belief. Their banks are coated in many places 

 with a white deposit, or efflorescence, called salitre ; whilst the Aconcagua and Tunuyan — the 

 one a companion of the Maypu, and the other of the Mendoza, which pass through settle- 

 ments free from the goitre— have very little or no salitre on their banks. I took pains to bring - 

 home some of this efflorescence, and it is now in the hands of a chemist for analysis. There 

 are also with the principal part of my baggage and instruments — which were left in Val- 

 paraiso for shipment around Cape Horn — two bottles of the water of-tlie Mendoza, and two from 

 the Tunuyan. On their arrival they will be analyzed, and, it is hoped, will give some informa- 

 tion on this subject. 



A striking change had taken place in the appearance of the outlet at the Uspallata Pass, on 

 the Chilean side, between the time of my first and second journeys across it. On the former 

 occasion there were but two or three huts below the Guardia Vieja, and around it there was no 

 sign of cultivation ; whereas, on the latter, instead of the one lonely hut at that place, there were 

 quite a number, and several small farms ; and from there to the valley of Santa Eosa there was 

 almost a continuous line of farms and houses. 



My expenses from Mendoza to San Jose and back, by the Portillo Pass, were eighty dollars, 

 exclusive of food ; and from Mendoza to Santiago, by the Uspallata Pass, fifty-four dollars. In 

 the first case I had only two light trunks ; and in the last, two loads and a half of baggage. 



It may be proper to remark, that the accompanying map (No. 9) is compiled from others, 

 except in the immediate vicinity of my road, where I have corrected it by observations. The 

 map of the two mountain passes (No. 8) is entirely from observations ; that of the Portillo 

 Pass having been planned from estimated distances uncorrected, but the Uspallata Pass having 

 the estimated distances corrected by positions astronomically determined. 



I left Valparaiso by the English mail-steamer of the 15th of January, proceeded to Panama, 

 and, after an unusual and harassing detention on the isthmus, returned to the United States by 

 the first steamer. 



Appended I give a table of the distances paid for on the post-road from Kosario to Mendoza. 

 I have the honor to be, very respectfully, your obedient servant, 



AKCH. MacEAE, 



Lieutenant U. 8. Navy. 



Lieut. J. M. GiLLiss, 



Supt. U. 8. N. Astronomical Expedition. 



