200 PecJcham and Linton — Trinidad Pitch. 



These observations apply with equal force to the ingredient 

 of the mixture denominated " organic matter not bitumen." In 

 the five specimens of commercial lake pitch the average amount 

 of this material is 10*651 per cent. The extremes of variation 

 include 1*482 per cent, which is 14*8 per cent or nearly one- 

 sixth of the average amount present. The smallest amount is 

 found in the average pitch from near the center of the lake, 

 yet No. 17, which was picked up from under the feet of the 

 men who were loading the tram cars on the west side of the 

 tramway near the middle, contains nearly 12 per cent. This 

 average lake pitch is found where the mass is in constant 

 motion from escape of gas. Here there is no organic matter 

 added by vegetation to the amount originally found in the 

 pitch. The growth of vegetation upon and in the pitch itself 

 is the source from which the excess of organic matter found in 

 the lake pitch taken from points outside the center and from 

 the so-called land deposits is derived. As this excess consists 

 mainly of coarse roots it is removed by refining, so that when 

 the pitch is ready for use the difference in the organic matter 

 has largely or entirelv disappeared. See numbers 2 and 19, 

 8 and 20. 



Table No. 2 shows the results of a comparative examination 

 of the bitumen contained in the different samples without 

 regard to the amount present. The first division of this table 

 shows the percentage of the crude pitch dissolved only by 

 petroleum ether, boiling spirits of turpentine and chloroform 

 respectively. The middle column gives the percentage of the 

 total bitumen in the crude pitch. The next three columns 

 give the percentages of the total bitumen present dissolved 

 only by petroleum ether, boiling spirits of turpentine and 

 chloroform respectively. The last column shows the percent- 

 age of the total bitumen dissolved by boiling spirits of turpen- 

 tine. This item is represented by adding together the items 

 of the first and second columns, as all of the material that is 

 dissolved by petroleum ether is soluble in boiling spirits of tur- 

 pentine. A comparison of these numbers along each hori- 

 zontal line shows that there is no necessary connection between 

 the amount of crude pitch dissolved by petroleum ether and 

 the quality of the total bitumen. As an example, in No. 1, 

 which is a land pitch, 100 parts of bitumen are mixed with 

 very nearly 100 parts of sand and organic matter, not bitumen, 

 while in No. 9 from the center of the lake 100 parts of bitu- 

 men are mixed with about 92 parts of foreign matter. Now 

 while the percentage of crude pitch dissolved by petroleum 

 ether from No. 1 is 2*333 per cent less than the percentage of 

 No. 9 dissolved by the same menstruum, the proportions of the 

 total bitumen dissolved in the two cases are almost identical, 



