376 ANNUAL REGISTER, 1800. 



59 brought over. 



50 brought forth on the SOth day. 



21 ■ on the 31st day. 



9 on tlie 33d day. 



139 



The difference between the two extremes, in these animals, was 

 7 days. 



M. Tessier proposes to make similar inquiries respecting the hatching 

 of the eggs of birds ; on which subject, he mentions a curious observation, 

 made by M. Darcet, namely, that, of the eggs of the same brood, 1 was 

 hatched on the 13th day, 2 on the 17th, 3 on the 18th, and 5 on the 

 19th and SOth days; there were some others which were not hatched. 



Experwients respecting the CircU' 

 lation of the Sap in Trees. By 

 M. Coulumb ; from the Journal 

 de Physique. 



TOWARDS the middle of A- 

 pril, in the year 1796, I had 

 several large Italian poplars cut 

 down ; the sap had already begun 

 to rise, and the trees were covered 

 with budding leaves. As I was 

 overlooking the workmen, I ob- 

 served that one of these trees, which 

 was already divided to within a 

 few lines distance from the axis of 

 the tree, made a noise, when cut, 

 similar to that produced by air, when 

 it rises in large quantities and in 

 small globules, through the surface 

 of a fluid. By having several more 

 trees, of the same sort, felled, I 

 observed that this noise, as well as 

 the flowing of a very limpid and 

 tasteless water, took place only when 

 the trees were about half cut 

 through. I afterwards caused se- 

 veral trees to be cut through, in a 

 circular form, so that they were 

 only supported by a cylinder, of 

 from 30 to 40 millimetres in dia- 

 meter, at the axis of the tree. — 

 These trees, as they fell, frequently 



remained joined to this axis, by 

 fibres partly broken ; at which time, 

 bubbles of air were seen to come 

 out in great abundance ; insomuch 

 that the quantity of air which came 

 from them was incomparably great- 

 er than that of watery sap ; but the 

 last-mentioned fluid was perfectly 

 limpid and tasteless. 



From this experiment, I suspect- 

 ed that, in large trees, the sap rises 

 perceptibly only near the axis of the 

 tree which forms the medullary 

 canal leading to the youngbranches, 

 or at least in the vessels which are 

 contiguous to this canal. 



In order to try if my conjecture 

 was true, I immediately caused four 

 or five poplars, of from three to 

 four decimetres in diameter, to be 

 pierced with a large auger: the 

 opening was made at the distance 

 of one metre above the ground, and 

 directed horizontally towards the 

 axis of the tree. I observed that, 

 till within the distance of two or 

 three centimetres from the centre 

 of the tree, the spiral screw of the 

 auger was scarcely wetted ; but, as 

 soon as it had arrived at this dis- 

 tance from the axis of the tree, the 

 water came out iu abundance ; and 



" 



