AS- 



star, determined by the bottom microscope onl}'^ would not 

 preserve, in different temperatures, the same relation to the 

 zenith distance determined by the mean of the three micros- 

 copes. No alteration however is observed to take place. 

 Thus for a Lyrae the following are the corrections to be ap- 

 plied to the zenith distance by the three microscopes to give 

 llie zenith distance by the bottom microscope only. 



This indicates no change of figure, and the same is ob- 

 served with respect to other stars. In a. Aquilae, for in- 

 stance, the quantity to be applied to the mean of the three 

 microscopes to give the result by the bottom microscope 



only = + 1 nearly, and no material change occurs in dif- 

 ferent temperatures. * 



Besides if this parallax arise from some deception, it 

 ought to appear in all stars sufficiently near the zenith, so 

 as not to be afteeted by uncertainty in change of refraction. 



• The difference between the mean of the three microscopes and the bottom aakros^ 

 cope is no where greater than for a Atjuilse. 



