76 SCIENCE PROGRESS 



is a great advantage, but the form has entirely disappeared. 

 Another Egyptian form was the iron sickle (fig. 8), with a 

 trough groove to hold a strip of steel teeth ; this was adapted 

 from the old Egyptian wooden sickle with flint saws inserted, 

 and when steel was valuable it was a great advantage, yet it 

 entirely died out from use. The use of saws and crown drills 

 with fixed teeth of corundum or gem stones, for cutting 

 quartz rocks, was the regular system of work in Egypt 6,000 

 years ago, and in Greece 4,000 years ago. The cores produced 

 were so perfect and clean-cut that, as Sir Benjamin Baker said, 

 any engineer would be proud to turn out such good work with 

 the best diamond drills. The saws were over eight feet long, 

 sawing blocks of granite r ]\ feet long. 



This splendid work was quite forgotten, the Roman had no 

 such grand tools, and some thousands of years passed before 

 such means were reinvented fifty years ago. 



In other cases we can trace the gradual evolution of a tool 

 down to the present day. The carpenter's saw was at first 

 merely a blade roughly hacked on the edge ; by 4,500 B.C. it 

 had regular teeth, sloping equally both ways ; by 900 B.C. 

 the Italian gave a rake to the teeth to make them really cut in 

 one direction, instead of merely scraping as before. No ancient 

 saw, however, had a kerf, cutting a wider slit than the thickness 

 of the blade ; we do not know when that was invented in the 

 Middle Ages. The Egyptian used a push-saw as the earliest 

 form ; the pull-saw was the only one in the West and the Roman 

 world ; the push-saw came back into use in the last few cen- 

 turies, though the pull-saw in a frame is still universal in the 

 East. The world did without shears for many ages, cloth 

 being cut with a rounded-blade knife (fig. 34). About 400 B.C. 

 the mechanical genius of Italy invented the shears, which in two 

 or three centuries more were fitted to the fingers, and thus 

 started the scissors. The snuffers in Exodus is a mistranslation ; 

 the early tools for trimming a lamp were a small knife and 

 pair of tweezers to trim the wick, and a point to part the strands. 



In some cases it is curious to see how long men remained on 

 the brink of an invention. Copper wire was made by cutting 

 and hammering, f rom 5 , 5 00 b . c . , y et the drawing of wire remained 

 unknown for 6,000 years or more. When the first drawn wire 

 was made is not yet fixed, but it seems to have been unknown 

 to the Romans. Thick beaten wire was made into chain with 



