J S2 Uoyal Society of London. 



March 5. Earl of Morton \n the chair. — A paper by 

 Mr. Rigo was read, containing a proposal for a new com- 

 pensation pendulurn. The failure of all former attempts tq 

 construct pendu'ums not subject to the changes occasioned 

 by temperature, induced the author to make some experi- 

 ments with various metals, in the course of which he^ disco- 

 vered, that of all the '.nodes of compensation, that of triangle? 

 was the best, and- accordingly he constructed on^ of trian- 

 gles, two sides of which were composed of small steel bars^ 

 and the base of brags or zinc, which expands two times 

 more than steel, and hence the expansion of the sides wa^ 

 duly counteracted by the expansion of the base. In this 

 manner, he alleged, pendulums might be constructed of 

 two, three; or more series of triangles, that would continue 

 the same length throughout all climates and seasons. The 

 same idea, the author acknowjedc! d, had occurred toothers. 



March 12. The Right Ho-.iourable Sir J. Banks, Bart., 

 President, ha^'ing recovered fr'>m his indisposition, resumed 

 the chair. — A paper by Dr. Wollaston, " On Fairy Rings,'- 

 was read. Those deep green circles of coarse grass seen in 

 humid meadows and pasture-ground have occupied the at- 

 tention of several p!iilosophers, in order to be enabled to 

 give a satisfactory physical explanation of their origin, pro- 

 gress, and final termination. Dr. VVollasto^ having ob- 

 served that fungi were always found on the exterior border 

 of these rings, thence inferred, that they originated in the 

 exhausted state of the soil, which could only nourish agarics, 

 instead of more perfect vegetables. It yet remains, how- 

 ever, to be decided whether this circumstance be an effect or 

 a cause of the phscnomena in question. 



March 1 9. The President in the chair.— A part of an in- 

 terestinp' paper, by captain Flinders, (containing also some 

 corrections of his former one) on the dip of the magnetiq 

 needle, was read. The captain detailed a great number of 

 observations, made at different times, on the variations of 

 the needle according to the direction of the ship's head iri 

 different latitudes. — The society then adjourned, on account 

 6f the holidays, till the gth of April. 



