306 PHILOSOPHICAL TRANSACTIONS. [aNNO 1793. 



Tatties are a kind of mat, made of fresh green bushes, or long roots, like 

 snake-root, they are affixed to the door or window frames, and kept constantly 

 sprinkled with water. The degree of cold produced by their means is supposed 

 to be in proportion to the heat of the wind which passes through them, as on 

 that depends the quantity of evaporation. 



Xlf. Meteorological Journal, kept at the apartments of the R. S,, by order of 

 the President and Council, p. 133. 



JlIJ. a Description of a Transit Circle, for Determining the Place of Celestial 

 Objects as they Pass the Meridian. By the Rev. F. JVollaston, LL. B.y 

 and F.R.S. p. 133. 



An instrument which in one observation is capable of giving with precision, 

 both the right ascension and declination of celestial objects, has always appeared 

 to me, says Mr. W. one of the desiderata in astronomy. Thougli I had often 

 considered the various methods practised for ascertaining each, and considered 

 how I could contrive to make one instrument answer both purposes ; I never 

 could satisfy myself in what way to effect the one, without destroying the ac- 

 curacy of the other ; till one evening, at a meeting of our Society in the begin- 

 ning of 1787, Mr. Ramsden mentioned to me his idea of reading off the divi- 

 sions of an instrument, by a microscope having a micrometer in the field of view, 

 which, being detached from the limb, could examine with accuracy the distance 

 of the nearest division from a fixed point. It occurred to me immediately, that 

 this was the thing I wanted : because a circle attached to the telescope of a tran- 



