dO PHILOSOPHICAL TRANSACTIONS. [ANNO 178], 



Mars passes over in K), 15, 20 m minutes respectively. He exposed them to 

 several persons unacquainted with his designs, and found, that not one of them 

 made a single mistake in saying whether the point was, or was not, in the centre 

 of the circle, and which way it deviated from it. As the direction of the mo- 

 tion of a spot on Mars is known, he thought the persons who were to judge of 

 the place of the points were entitled to be acquainted with the line in which they 

 were placed, which for that reason was always to the right and left only. The 

 points that answer to the excentricity of 15' and 20' are indeed so visibly out of 

 the centre, that we may safely say, that any mistake, in estimating the time of a 

 spot on Mars coming to the centre, cannot well exceed a quarter of an hour at 

 the outside. 



As for the 3d and last occasion of error, the time itself, he thinks may be 

 depended on to a few seconds; but the observations of the year J 777, indeed, 

 are far from having the same advantage. He was not then provided with an al- 

 titude instrument, therefore set his clock by a good sun-dial, with the equation 

 of time contained in the Nautical Almanac, and found it to agree generally to a 

 minute or 1 with the time calculated for the eclipses of Jupiter's first satellite, as 

 he deduced it for Bath from the Nautical Almanac. However, it was certainly 

 liable to an error of several minutes; therefore, allowing no less than 10 m for the 

 clock in 1777, and 20 m for an error in estimating the situation of a spot in 1779, 

 it will both amount to half an hour; then, if we take a mean of the 3 numbers, 

 by which we have divided the 3 biennial periods, we have 766*^; an( l half an hour 

 divided by 766-^, will therefore give us the quantity to which, it seems, can 

 amount, all the uncertainty in the sydereal diurnal rotation of Mars, which 

 is 2 S .34. 



XI. Of the Termites in Africa and other Hot Climates. By Mr. Henry 

 Smeathman, of Clement's Inn. p. 139. 



The size and figure of the buildings of these insects have attracted the notice 

 of many travellers, and yet the world has not hitherto been furnished with a 

 tolerable description of them, though their contrivance and execution scarcely 

 fall short of human ingenuity and prudence ; but when we come to consider the 

 wonderful economy of these insects, with the good order of their subterraneous 

 cities, they will appear foremost on the list of the wonders of the creation, as 

 most closely imitating mankind in provident industry and regular government. 



These insects are known by various names: they belong to the termes of Lin- 

 neus, and other systematical naturalists: by the English, in the windward parts 

 of Africa, they are called Bugga Bugs ; in the West Indies, Wood Lice, Wood 

 Ants, or White Ants. By the French, at Senegal, Vague- Vagues ; in the West 

 Indies, Poux de Bois, or Fourmis Blanches. By the Bohns, or Sherbro people, 



