Notices respecimg Ne*io Books. 295 



interesting, but in what respect it will render the British arc more 

 valuable is not apparent, unless for the general reason that every 

 new datum for the figure of the earth may be said to increase the 

 value of all the foregoing. Captain YoUond says because it will be 

 reducible to the same unit of measure. Are we to infer from this that 

 the meridional arcs measured in France, Germany, Russia, and other 

 countries are not reducible to the same unit with those measured by 

 the compensation apparatus ? If so, both the British arc and the Cape 

 arc will be of comparatively little value ; for assuredly the figure of 

 the earth wUl be determined with greater certainty from all the conti- 

 nental measurements taken together than from those two alone, what- 

 ever advantage may be attributed to the use of the compensation bars. 

 But surely there can be no greater difficulty in determining the re- 

 lation of the French toise, or metre, to the standard of the Irish base 

 than in determining the ratio of the 6-inch scale to the 10-foot bar. 

 All the arcs whose standards have been preserved must be suscepti- 

 ble of reduction to the same unit of measure ; and we trust Captain 

 Yollond will not think it necessary (if the matter depend on him) to 

 defer the publication of the triangles connected with the meridian 

 until the results of the Cape measurement are known, on the ground 

 that there are no other arcs with which our own is directly compa- 

 rable. We would remind him that the Indian arcs measured by 

 Colonel Everest (of which, by the way, he makes no mention) are 

 not less important than the Cape arc will be for the determination 

 of the figure of the earth. They depend on bases which have been 

 measured with similar apparatus, and Captain Yollond has himself 

 already compared their standards with those of the Ordnance Survey. 



But although the observations may possibly be completed in the 

 course of the present season, it does not follow that they will 

 be speedily communicated. " Major-General Colby's retirement 

 from the superintendence of the Ordnance Survey at the end of the 

 present month (March 1847), leaves me unable to state the arrange- 

 ments which are likely to be made for publishing the mass of Tri- 

 gonometrical Observations made by the Survey Department during 

 the last thirty- six years." 



To those who have been looking forward to the termination and 

 publication of the results of this great national undertaking, the an- 

 nouncement we have just quoted is not calculated to aiFord much sa- 

 tisfaction. The last account we have of the trigonometrical observa- 

 tions was published in 1811. Since that year the survey has been 

 in progress ; it is said that upwards of a million and a half has been 

 expended on it : and arrangements are still to be made for the pub- 

 lication of the observations which have been accumulated in the 

 long interval*. That the work will be found to have been executed 



• The subject acquires an immediate interest, from the project which 

 has been entered upon of an Ordnance Survey of the metropolis for the 

 alleged but unexplained purposes of the Sanitary Commission. From the 

 discussion of this [)rojcct in the House of Commons, March 24, on the 

 Ordnance Estimates it would aj)|)ear that no one could tell what it vvas 

 to cost, how it was to be paid for, or wliat purpose it was to answer. 



