248 On the Erroneous Geographical Position of 



do very well. If much longer, when inserted into the holes 

 made by the signal staves, they protrude above ground, and 

 are thus liable to be removed by accident or design. If short- 

 er, they drop too far into the holes, and cannot be easily ex- 

 tracted. The names of the stations are marked on these pins 

 by notches, as shewn in Loudon's Encyclopaedia of Gardening. 

 To recapitulate ; the advantages afforded by the method of 

 co-ordinates are as follows : The errors acquired in the field 

 operations are all corrected, and the amount of error in every 

 polygon is made apparent in the form of a simple quantity. 

 The area is deduced from corrected data, and the plans are 

 also protracted from corrected data ; and the positions of the 

 points being determined by independent quantities, there can 

 be no accumulation of error in them. It is impossible that a 

 blunder in the field-work pass into the subsequent operations. 

 From the uniformity and simplicity of the notation, all the cal- 

 culations, as well as the measurements, can be referred to, and 

 examined at any subsequent period. Besides, the scheming of 

 the field operations is more easy, and the time occupied in them 

 and in the house work is less than by the old methods. 



KIRKALDY, \7th March 1836. 



On the Erroneous Geographical Position of many Points in the 

 Frith of Clyde. By WILLIAM GALBEAITH, Esq. M. A. 

 Teacher of Mathematics, Edinburgh, M. S. A. * 



THERE are few branches of knowledge more generally inte- 

 resting than the sciences of Geography, Astronomy, and Navi- 

 gation. From the combined progress of these departments of 

 human knowledge, many new and interesting discoveries in dis- 

 tant portions of the earth's surface have of late years been 

 made, and their exact position determined with considerable pre- 

 cision. When this is admitted with regard to the more distant 

 countries of the globe, it is naturally to be expected that the 



* Read before the Society of Arts for Scotland 7th December 1836. 



