78 Land Magnetic Observations, 1911-13 



September 2, 1912, and arrival at Timbuktu, May 12, 1913, is here charged to the trans- 

 Saharan work. While perhaps the river travel from Gao to Timbuktu, occupying 19 

 days, ought not to be so charged, the character of interior African travel is so uncertain 

 that a statement of time or expense involved is of little assistance as a guide to undertaking 

 similar work or even the same work some other time. The assignment of 19 days addi- 

 tional to the trans-Saharan trip then creates no difficulty. Using the above dates, we have 

 an interval of almost 85 months, or 252 days. Seventy-two stations were occupied, making 

 an expenditure of 3^ days per station; 76 stations were occupied, if partial stations arc 

 counted. Preparations at Algiers consumed 2 months; the danger from Berbers used up 

 13 days; time lost in resting the animals consumed, not counting 1-day stops, about 15 

 days ; while a sand storm accounted for 4 days. It is to be noted also that in this interval 

 special declination observations were made at Algiers; a 24-hour series of declination 

 observations was made twice and a 12-hour series once; and complete intercomparisons 

 of instruments were carried out. 



A fair assignment of cost to the Saharan work is $7,789. This includes the return 

 transportation cost of the European interpreter, but not the cost of return to Biskra of the 

 two natives, Josef ben Saad and Isa ben Saad. It is evident that the entire cost of trans- 

 porting home all three of these men can not fairly be assigned to the less rigorous travel 

 south of Timbuktu. This brings the average cost per station in the Sahara to about 

 $108. About 1,800 miles of desert were traversed by camel caravan. As 72 stations 

 were occupied, there was one station for every 25 miles of travel. 



Magnetic conditions. In the gorge of Tibratne, and again throughout the Tuareg 

 country, and at several other places, the rock, sand, and gravel of the surface were found 

 extremely magnetic. A bar-magnet wrapped with paper and drawn through the sand 

 collected particles almost as readily as if the same experiment had been made with iron 

 filings. The high static charges, encountered at several places, have already been men- 

 tioned in the itinerary accovmt. 



Assistance rendered. It is a pleasure to record here the great interest taken in our work 

 by the French officers, civil and military, that were met, as also to acknowledge gratefully 

 the special pains taken by them to assure, as far as possible, the success of our work. Their 

 effective and cordial aid at all times made possible the successful conclusion of the expedi- 

 tion. To General Bailloud, then commanding the 19th Army Corps of France, the expedi- 

 tion is under special obligations, not only for official assistance rendered but also for personal 

 kindness extended. To him we are indebted for the militarj^ arrangements that furnished 

 protection to the party ; to him again we are under obligations for the use of a recent ly invented 

 wireless receiving-apparatus at In-Salah, which allowed us from that remote station in the 

 Sahara to obtain time signals from the Eiffel Tower, Paris. To Commandant Meynier of 

 the Colonial Staff we are under special obligations for the advice and assistance furnished, 

 out of his rich experience, in the preparation and equipment of the party at Algiers. Our 

 comfort and safety from the physical features of the desert may largely be assigned to his 

 care and solicitude. 



Our gratitude is also due the Governor-General of Algeria, M. Lutaud, for great ])er- 

 sonal courtesy and interest shown in the work. We are under great obligation to all the 

 officers and officials of Timbuktu, for courtesies received at various times, especially to 

 Lieutenant Colonel Sadorge, commandant of Timbuktu, who, in addition to numerous 

 kindnesses shown, furnished steel boats, with crews of military men, for our ascent and 

 descent of the Niger. 



We are under particular obligations also to Mr. Mason, American consul at Algiers, 

 and to his clerk, Mr. Boisson. 



The longitudes of the stations, as given in the Table of Results, depend upon chro- 

 nometer and watch rates. The corrections of our timepieces were determined by compari- 



