V. CLOCKS AND SUNDIALS. 



415 



2. The mural form. This instrument only differs from the preceding in its 

 method of mounting, which secures greater accuracy ; and a small telescope 

 is added, for the purpose of obtaining a finer reading of all the observations. 



(One of these instruments is mounted upon the balcony outside. Upon 

 looking into the telescope (which must be shifted up or down until the images 

 are seen) the two apparent suns will be visible in the field of view ; these will 

 gradually approach as above described, and will be superimposed at the instant 

 of apparent noon.) 



3. The universal form. This is mounted upon an axis, which by means of 

 a divided "latitude " scale can be placed parallel to the earth's axis. It has 

 also another scale, divided from three hours before, to three hours after noon, 

 and true time may be obtained at any quarter of an hour within this interval. 

 The instrument is furnished with a compass, but this should not be used where 

 more accurate methods of setting it can be employed. 



1843b. Astronomical Signaller for the purpose of giving 

 notice of the approach of stars, or any required point in R.A. to the 

 meridian. E. Dent and Co. 



1844. System of Patent Electro-Sympathetic Clocks. 



James Ritchie and Son. 



Fig. A. 



