va 
1815.) On the Uses of the Dorsat Vessel. 43 
different ramifications to the abdominal muscles and the pulmonary 
trachee. The second branch sets out simple, but speedily divides 
into two branches, each much larger than the common trunk. Near 
the point where these tracheze unite to furnish a single branch to the 
_pulmonary trachez, they send off two branches, the superior of which 
goes to the superior branch, and the inferior to the inferior. Thus 
on each side of the abdomen are disposed'the five other common 
trunks which open into the stigmata, so that these six orders of 
trachez correspond to the openings of these parts. As there are in 
all 16 branches on each side of the abdomen, the arterial trachee 
give on each side three large simple branches, which go to the 
pulmonary. They communicate with each other by means of small 
ramifications which they send to each other. All these. principal 
branches have constantly a transverse direction. The bundle of 
tracheze that go to the organs of generation proceeds from the first. 
double branch. What is remarkable in this respiratory apparatus is 
the great diameter of all the abdominal traches, especially those 
with double branches. ‘These trachee are so large, and so close 
together, that they form a kind of envelope round the organs con- 
tained in the abdomen. 
ArticiteE VIII. 
An Essay on the Shapes, Dimensions, and Positions of the Spaces, 
in the Earth which are called Rents, and the Arrangement of the 
Matter in them. By Mr. John B. Longmire. 
(Continued from vol. v. p. 281.) 
The junctions of bended-tabular Rents. 
The horizontal direction of any rent is not parallel to this diree- 
tion of all the other rents in a formation ; and as the lengths of rents 
in general are much greater than the distance between any two 
contiguous rents, many rents must be joined to others, ‘Two of the 
junctions of bended-tabular rents Iam now to describe. 
Bended-tabular rents, according to the difference in their posi- 
tions, are joined together in their horizontal directions, and in 
those which are at right angles to them, whether angular er per- 
pendiculary The junctions of these rents, in common language, 
are called crossivgs: and one rent is said to intersect and to cross 
apother; and to disturb it by throwing or heaving it, either up- 
wards or downwards, in horizontal junctions, and either to the right 
or left hand, in angular junctions, 
1. Of horizontal Junctions. 
When the sides of one rent, say the rent A, fig, 1, PlateXXXV., 
2 
