230 



ing telescope. Upon these it is unnecessary to dwell. The 

 changes of position are to be determined by referring the teles- 

 cope, from time to time, either to a distant fixed mark, or to a 

 fixed collimator. In the Magnetical Observatory of Dublin, 

 the telescope of the transit instrument is used as a collimator, 

 and thus the position of the reading telescope is referred imme- 

 diately to the astronomical meridian. 



Sir Robert Kane laid before the Academy some specimens 

 of the series of maps now being prepared in the Museum of 

 Irish Industry, illustrative of the distribution of the values of 

 land in Ireland. The principle of the construction of these 

 maps was described by Sir Robert Kane to consist in the 

 reduction of the numerical results of the Government valuation 

 of Ireland, now in process of publication, under the direction 

 of Mr. GriiBth, to such system of classification, indicated by 

 characteristic colours, as would show the manner in which the 

 soils of different financial values are distributed over the coun- 

 try. The specimens laid before the Academy comprised two 

 sets of maps, of which the one showed the registered valuation 

 of townlands ; the second, the values of groups of townlands 

 reduced to an average of value. The method employed was 

 the following. Sir Robert Kane, having found by consulta- 

 tion with experienced agriculturists that the unit of difference 

 of value might be taken as sufficiently small for practical pur- 

 poses at two shillings per statute acre, reduced the values of 

 townlands to a scale of ascending rates, from zero to thirty-six 

 shillings per acre, and then, having transferred to the county 

 index maps of the Ordnance Survey the boundaries of town- 

 lands, which are engraved only on the maps of the six-inch 

 scale, those are coloured with tints respectively indicative of 

 the values, and thus a pictorial representation of the distribu- 

 tion of the different classes of land is obtained. As the map 

 so formed becomes, however, very detailed, the number of 

 tints very numerous and very much intermingled, and hence. 



