Among the saws that are neither loops nor disks are three of the most common hand saws used by the carpenter: the ripsaw, the crosscut saw, and the backsaw.
Ripsaws are used for cutting wood with the grain, crosscut saws for cutting across the grain.
To provide space for the cuttings, M-shaped teeth with gaps (gullets) between them were developed; this tooth conformation, first noted in the mid-15th century, is still used in modern crosscut saws manufactured for coarse work and for cutting heavy timber.
The ripsaw teeth have cutting edges that are at 90° to the blade and act like a row of chisels; the crosscut has knifelike teeth that are set to alternate sides and cut two parallel lines on each side of the kerf, so that the wood in between is broken up.
On wood it can rip, crosscut, and make angle cuts.
Driving Simplon as two parallel tunnels with frequent crosscut connections considerably aided ventilation and drainage.
Finally, certain boards are crosscut with trimmers to square their ends and remove defects.
Depending upon the direction of the stresses applied during metamorphism, phyllite sheets may parallel or crosscut the original bedding; in some rocks, two stages of deformation, called precrystalline and postcrystalline deformations, can be distinguished on the basis of two orientations of definable surfaces in the rock.
Frame saws, in which a narrow blade is held in tension by a wooden frame, were exploited in many sizes, from the small carpenter's saws to two-man crosscut saws and ripsaws used for making boards.
The crosscut saw cuts across wood grain, and the rip saw cuts with the grain.
A third crosscuts dizzyingly between wartime London and the story of Emil Freireich, a doctor who suffered a Dickensianly miserable childhood and went on to a brilliant career, to show, one supposes, that triumphing over adversity is better than succumbing to it.Mr Gladwell's earlier books, particularly "The Tipping Point", his first, were genuinely thought-provoking.
