Jot the year 1868. 13 



it is therefore proposed to erect a circular building, with a 

 revolving roof, and Parliament will be asked for a vote for 

 this purpose. A small extension of the Observatory ground 

 has- been granted, thus enabling the telescope to be erected 

 in a position where it will command a full view of the 

 heavens without creating any disturbance on our magnetic 

 instruments by its too close proximity. 



You will remember that in my last address I mentioned 

 that a complete set of self-registering magnetic instruments 

 or magnetographs (similar to those used at Kew) were ex- 

 pected to arrive shortly. These duly arrived, they have been 

 erected and at work since November last, producing an 

 uninterrupted photographic record of all changes of the 

 forces of terrestrial magnetism. 



A wet and dry bulb thermometer and barometer, contin- 

 uously self- registering, on the same principle, are now being 

 constructed for us, and will probably be at work in the 

 course of a few months. The results likely to be obtained 

 from the adoption of self-registering instruments of this 

 kind can scarcely be too highly estimated, for the periodic 

 method of observing phenomena that are changing contin- 

 uously, could never satisfactorily admit of those close 

 deductions being made requisite to derive any practical value 

 from the observations. Variations of the forces measured 

 sufficient to establish or overthrow a supposed law may, and 

 doubtless do, often happen in the intervals between inter- 

 mittent observation, which, by the photographic or other 

 self-registering method, is indelibly recorded with true 

 relations to preceding and following variations. 



The Melbourne portion of the survey of the southern 

 heavens has made considerable progress ; the portion of the 

 heavens lying between the 150° 40' and 152° 46' parallels of 

 declination have been thoroughly surveyed, and the posi- 

 tions of 19,600 stars established. 



