36 SURVEY OF MASSACHUSETTS. 
“Number of the Length of first | Length of second | First differ- Second di€ | 
Comparison, - measu Lhe measure, ence. ference. 
11995.225 11995.450 | — 0.225 +225 
23994.307 23994.413 — 0.106 «119 
35991.383 35991.772 | — 0.389 +283 
47991.350 47991.638 | — 0.288 101 
§9991.266 59991.554|— 0.288; .000 
71991.325 71991.444| — 0.119 169 
95981,617 95981.886 | — 0.269 .150 
107981.560| 107981.665)— 0.105 164 
119981.242| 119981.552) — 0,310 205 
10| 131980.062 131980.360 | — 0,298 012 
11| 143979.732| 143980.046| — 0.314 .016 
12| 155974.794| 155975,128 | — 0.334 .020 
13| .167970.783| 167971.008| — 0.225 .109 
14| 179962.639| 179962.938 | — 0.299 074 
15| 203961.267| 203961.493 | — 0.226 .073 
16| 227960.220| 227960.355 | — 0.135 091 
17| 251960.280} 251960.300 | — 0.020 115 
18| 287960.554| 287960.276|+ 0.278 .258 
19| 299960.660| 299960.261/|+ 0.399 121 
20| 311960.715| 311960.261|+ 0.454} .055 
OANAHSAhWNWe! 
21| 347959.994| 347959.461| + 0.533 079 
22| 371959.892| 3'71959.182| + 0.710 ATT 
23| 386337.443| 386336.615/-+ 0.828) .118 
24| 428915.406| 428915.268| + 0.138 .690 
25| 467914.561| 467914.324 | 4+ 0.237| .099 
Total sum of all the differences, in inches, 3.523 
I would here remark, that our apparatus having been constructed upon principles 
entirely new, so far as it respects an application to works of this kind, we found consider- 
able trouble in our first attempts at measuring, and it was not until we had measured that 
portion of the line_represented by the column marked “ first measure,” beginning at the 
bottom, or No. 25, and extending as far as Nos. 19, or 18, or thereabouts, that we had per- 
fected all the adjustments of our apparatus. This portion of the line was, moreover, 
very uneven, or hilly, so that we were frequently obliged to measure over ridges upon 
inclinations of from 3 to '71 degrees. The combination of all these troubles and difficulties 
may account for the large errors apparent in that part of the measurement. Since we 
found less difficulty in measuring after we had perfected our apparatus, it is reasonable to 
suppose that the second column gives the most accurate measurement: but as the final 
results were so near alike, I have given equal weight to both. 
The above table contains the length of that portion of the base line which was mea- 
sured with the fifty feet apparatus, to which is to be added 265.466 inches, which 
were taken with the beam compass. Before making the addition, I would observe that 
the exact length of the fifty feet measure, as determined by the Massachusetts standard 
after the measurement of the line was completed, was found to be only 599.998 inches. 
Therefore, a2 mean of the measures exhibited in the table, 
reduced 10 Massachusetts standard, is equal to. ...++- 467,912.882 inches, 
Add for the measure taken with the beam compass,......- 265.466 «+ 
Whole length of base line,..... + . 468,178,348 
