the return journey on March 18, observ- 

 ing the barometer at short iutervaJs for 

 an hour to two before leaving Meadow 

 VaJe, and after reaching Broken Bluff. 

 From these observations we computed 

 the difference of height to be from 420ft. 

 to 470ft., the uTLcertainty arising from 

 our imperfect knowLedge of the variations 

 of preissure due to atmospheric changes 

 during the day. Combining all the obser- 

 vations on both days, we took Meadow 

 Vale to be 430ft. above Broken Bluff. The 

 height of Meadow Vale is therefoTe about 

 4.730ft., but this result, for the reason 

 stated, is more uncertain than that for 

 the first s:tag«. 



The third and final stage was froiii 

 Meadow Vale to the highest point of the 

 northern part of the mountain. The 

 miean of oloselv agreeing ascending an(i 

 descending readings gave a difference of 

 •height of 440ft. The northern summ l 

 -therefoi-e appears to be about 870ft. above 

 Broken Bluff. In 1906, with another m 

 strument, the mean of ascending and de- 

 scending readings taken on the same day 

 between B.roken Bluff and the noi'thern 

 summit was 860fr. Adding this number 

 to the height of Broken Bluff, 4,3O0ft., ■(\o 

 find that the height of the northern sum- 

 mit is in round figures about 5,150ft. if 

 this result be correct, the northern sum- 

 mit is therefore about 150ft. higher thai, 

 the trigonometrical station at the .south- 

 western corner of the mountain, and 

 obout 70ft. higher than Cradle Mountain, 

 and therefore appears to be the highest 

 knoviTi point in Tasmania. 



This reisult cannot, however, be accept- 

 ed as final. In spite of the close agree- 

 ment between the obseTv.ations made m 

 1SW6 and those of 1907, we cannot be quite 

 certain that there are no hidden sources 

 of error which might vitiate the result. 

 Such errors are of two classes — the firsc, 

 those due to the necessary im per feet ioiio 

 of the aneroid as .a means of measuring 

 pressure, the second those due to diurnai 

 and irregular atmospheric changes of 

 pressure taking place whilst we were go- 

 ing from one point of observation to an- 

 other. Of the first class the phenomenon 

 of elastic fatigue, also knowTi as "lag" 

 or "hysteresis" is the most usual source 

 of error. For such small differences of 

 altitude as we were measuring, this is 

 not very great, and we took sufficient read- 

 ings to eliminate it. There are, however, 

 other souroeis of uncertainty, such as 

 change of index error, against which we 

 could take no precaution. Of the second 

 olass of errors the luicertainty due to ir- 

 regular atmospheric changes may affect 

 the second stage of our woirk, but not, we 

 think, the first and third stages. As to 

 the regular diurnal changes we have no 

 information which will enable us to 

 supply a satisfactory correction. 



As a check upon the determination by 

 aneroid, we book an altitude observation 



with an Abney level. From the northern 

 summit the trigonometrical sitation had 

 a depression of about three-quarters of a 

 degree. The distance apart of the two 

 points is from six to seven milies. Aftet 

 allowing for a pos-sible observational error 

 of from 20 minutes to half a degree, we 

 find that the northern summit is at the 

 least from 100ft. to 200ft. above the tri- 

 gonometrical station, so that its heiglit 

 app^eairs from the Abnev level observation 

 to lie between 5,100ft. and 5,200ft. 



We hope to be able next suinmer to 

 make a small triangulation on top of the 

 range, and so determine within a foot or 

 two the differemce of height of 

 the two summits. We think it well, 

 however, to place on record at once the 

 results of our preliminary work. 



The question may be raised : If, as our 

 observations suggest, the northern sum- 

 mit is the highest point on the range, and 

 probably the highest point in Tasmnaia, 

 why is not this fact recorded on the 

 maps compiled from the trigoaiometricai 

 survey of the island? Such records as 

 there are of the work of this survey are 

 not in a condition to be readily intelli- 

 gible to a casual inquirer, but we under- 

 stand that they do not contain any ob- 

 servations of the .northern summit. Sev- 

 eral reasons, however, suggest the^naselves 

 why it was unlikely that any observations 

 of it should be made, even if, as wiaa 

 doubtless the case, its great height wa3 

 noticed. The station on Ben Lomond 

 formed part of the principal network of 

 triangles which connected the base at 

 Ralph's Bay with the base of verification 

 at Longford, and which was the basis of 

 the secondary tiiangulation from which 

 the maps of Tasmania are compiled. When 

 the principal triangulation had been ex- 

 tended northwards ais far as Miller's Blufi 

 (on the Great Western Mountains), and 

 Mount Connection (on the Eastern Tiers 

 midway between Ross and Swansea), it 

 wa's necessary to choose a third point to 

 the north, which with these two points 

 would form a well-conditioned triaingle. 

 It so happens that the present trigono- 

 metrical station forms a triangle which 

 is very nearly equilateral, and, is, the(r&- 

 fore, well suited to be a part of the 

 principal triangulation. If the northeirn 

 summit of the Ben Lomond range had 

 been chosen, the triangle formed by it 

 with the two mountains mentioned would 

 not have had quite such a good shape, 

 and it would probably liave been found 

 that Mount Oooinection was invisible 

 from it. Further, in choosing the prin- 

 cipal stations of the survey, regard was 

 doubtless had to their subisequent useful- 

 ness in land surveying. The present tiigo- 

 nometrical station was clearly the better 

 for this purpose, for it is a conspicuous 

 object from the valleys of the South Esk, 

 the Macquarie, the Lake, and the Mean- 

 der Rivers, all o£ which "vallej's wei^ then 



