144 ESSAYS AND OBSERVATI ON^ 



kept of their force and dire(5lion, might 

 not fome ufetul difcovery be expe<5led on 

 comparing them? 



TouloufCi January 6.1^66. 



Doctor Wark carried this with him 

 from Edinburgh, with a refolution of ha- 

 ving corre(?:ed and enlarged it, from the 

 obfervations he had made on the efFe6l 

 of the great earthquake at Lifbon ; but, 

 growing weaker and weaker every day, 

 he was never able to efFedl it. Soon af- 

 ter he had communicated the above me- 

 thod of difcovering the ftrength and di- 

 redlion of earthquakes by water to an in- 

 genious gentleman at Lifbon, he found 

 it would be very uncertain, as water, e- 

 fpecially when expofed to the open air, 

 undergoes a fpeedy evaporation ; he there- 

 fore advifes, in place of water, to ufe mer- 

 cury, and to cover the vefTel with a piece 

 of tranfparent glafs, io that no dull may 

 enter. 



N. B. Dr Wark died on the •14th of 

 January, eight days after didat^ng the 

 above. 



Art, 



