March -29, 1895.] 



SCIENCE. 



349 



mal membniues — and consequeutlj' would 

 not readily escape from the blood-vessels, 

 notwithstanding the fact that they are held 

 in solution in the circulating fluid. On tlie 

 other hand, the passage of the tetanus anti- 

 toxin into the mother's milk would indicate 

 a continuous supply, otherwise the immu- 

 nity of the mother would soon be lost. Fur- 

 ther experiments ar(> i-equired to settle this 

 question in a definite manner, and also to 

 determine the exact source of the antitoxins 

 in the animal bodj' and the modtt^ operandi 

 of their production. 



Geo. M. Sternberg. 

 Washington. 



SEMARKING THE MEXICAN BOUNDARY. 



Mb. a. T. Mosman, assistant in the U. S. 

 Coast and Geodetic Survej', one of the com- 

 missioners on the part of the United States, 

 presented an interesting summary of the 

 work at a meeting of the National Geo- 

 graphic Society in Washington on the 8th 

 inst. 



At the initial meeting of the commis- 

 sioners for the two countries, it was agreed 

 that any of the old monuments recovered 

 should be taken as defining the line ; that 

 new monuments should be interpolated be- 

 tween them, so that no two monuments 

 should be more than 8000 metres apart, as 

 retjuired by the new treaty. The line had 

 been marked under the treatj' of 1853, by 

 52 monuments ; the commissioners found 

 38 of these standing in 1891. On the paral- 

 lels the new monuments mark the curve of 

 the parallel, but on the oblique lines the 

 monuments recovered were not accurately 

 located on the line Joining their extremities, 

 and the boundary on these lines as now 

 marked is, therefore, a broken line. Old 

 monuments were recovered at all imj)ortant 

 points on the boundary, including all points 

 where the line changed direction, but the 

 distances between them were unequal, and 

 in one instance exceeded 100 miles. The 



line from El Paso on the Rio Grande to San 

 Diego on the Pacific, 700 miles, is now de- 

 fined by 258 monuments. 



The field work required the redetermina- 

 tion of the geograi)hic positions of the old 

 monuments recovered, and presents some 

 interesting comparisons showing the facility 

 and certainty of modern methods. The 

 longitudes of the old monuments were de- 

 termined by Emory from transits of the 

 moon and moon culminating stars. In the 

 relocation the longitudes were determined 

 by the telegraphic method, connected with 

 the geodetic work of the Coast Survej' by 

 coast survey parties working in conjunction 

 with the commissioners. The greatest dif- 

 ference developed from Emory's positions 

 was 4' 34". 3 with other differences of 34" 

 and 54" and still smaller quantities show- 

 ing the old work to have been remarkably 

 good for the method. The latitude stations 

 in the new work were about 20 miles apart 

 over the whole line, and at each station an 

 azimuth was observed on Polaris near 

 elongation to start the direction for the new 

 tangent for the parallel and check the tan- 

 gent ending at the station. The latitude 

 observations were made with the zenith 

 telescope formerly used on the N. W. boun- 

 dary, but improved with new micrometer 

 and levels. The telescope has a focal 

 length of 826 mm., and the objective a clear 

 diameter of (57 mm. A new departure was 

 made in mounting the instrument on a 

 wooden pier constructed in a simple form, 

 readily transported. Its stability proved 

 as great as a brick or stone cemented pier, 

 as it was not uncommon to secure a whole 

 night's work without relevelling, and the 

 instrument invariably remained for several 

 houi-s with level correction less than one 

 div.^l".28. The probable errors of the 

 latitude determinations from the U. S. ob- 

 servers = ± 0".03 to 0".4. The Mexican 

 observations have not yet been received. 

 The plan of operations agreed upon required 



