A HISTORY OF SCIENCE 



were really borrowed from the Hindoos, with whom 

 the Arabs came in contact on the east. Certain of 

 the Hindoo alphabets, notably that of the Battaks 

 of Sumatra, give us clews to the originals of the 

 numerals. It does not seem certain, however, that 

 the Hindoos employed these characters according to 

 the decimal system, which is the prime element of 

 their importance. Knowledge is not forthcoming as 

 to just when or by whom such application was made. 

 If this was an Arabic innovation, it was perhaps the 

 most important one with which that nation is to be 

 credited. Another mathematical improvement was 

 the introduction into trigonometry of the sine the 

 half-chord of the double arc instead of the chord of 

 the arc itself which the Greek astronomers had em- 

 ployed. This improvement was due to the famous 

 Albategnius, whose work in other fields we shall 

 examine in a moment. 



Another evidence of practicality was shown in the 

 Arabian method of attempting to advance upon 

 Eratosthenes' measurement of the earth. Instead 

 of trusting to the measurement of angles, the Arabs 

 decided to measure directly a degree of the earth's 

 surface or rather two degrees. Selecting a level plain 

 in Mesopotamia for the experiment, one party of the 

 surveyors progressed northward, another party south- 

 ward, from a given point to the distance of one degree 

 of arc, as determined by astronomical observations. 

 The result found was fifty-six miles for the northern 

 degree, and fifty-six and two-third miles for the south- 

 ern. Unfortunately, we do not know the precise length 

 of the mile in question, and therefore cannot be assured 



14 



