340 



PHILOSOPHICAL TRANSACTIONS. 



[anno 1739. 



Latitude Longitude Variation 



north west west 



31" 39' 20" 13' 9° 49 



30 55 . 

 30 17 . 



.22 53 9 6 



.25 26 8 39 



.27 14 7 56 



30 1 .. 



30 1 27 54 6 



. . 30 20 7 



..33 12 8 



29 55 . . 



29 57 . . 



29 51.. 



28 55 . , 



29 8 40 7 



31 10 44 46 8 



31 7 46 45 4 



48 



41 







41 



30 42 49 



30 29 49 48 



30 31 52 



30 18 53 



30 23 55 



30 58 57 30 . 



37 9-- 



37 37 5 



39 28 5 23 



12 

 6 

 46 

 4 40 

 4 

 4 49 

 4 45 

 4 22 

 4 52 



10. 

 0. 

 0. 



.68 4 50 



Some Thoughts and Conjectures Concerning the Cause of Elasticity. By J. T. 

 Desaguliers, LL.D. F.R.S. N° 454, p. 173. 



Attraction and repulsion seem to be settled by the great Creator as first 

 principles in nature ; that is, as the first of second causes; so that we are not 

 solicitous about their causes, and think it enough to deduce other things from 

 them. If elasticity was admitted as a first cause ; as it is by some, it is thought 

 we should admit of too many principal causes in nature ; which is contrary to 

 the rules of good philosophy. Philosophers therefore have endeavoured to de- 

 duce elasticity from attraction, or from repulsion, or from both. It is observed, 

 that the same particles that repel each other strongly, will attract other particles 

 very strongly ; as apppears by many chemical solutions, especially by the 

 alternate solution and precipitation of metals in acid menstruums. Dr. Hales 

 has proved this many ways, in his vegetable statics and haemastatics. The 

 elasticity of air seems to consist wholly in the repulsive power of its particles, 

 which do not touch one another while the air is in its elastic state ; and if 

 those particles be brought nearer and nearer together, the efi^ect of their re- 

 pulsive force will increase, the air's elasticity being always proportionable to 

 its density by compression, which property will be preserved, though com- 

 pressed air be kept a year or two ; notwithstanding, Mr. Hawksbee, in his 

 Physico-mechanical Experiments, says, that air will lose part of its spring by 

 being very much compressed. But the air with which he tried it, must have 

 been filled with moist vapours ; and it is well known, that the steam of liquors 

 will lose its elasticity, especially where its heat decays. Dr. D. has kept several 



I 



