114 



• KNOWLEDGE ♦ 



[Aug. 8, 1884. 



lampblack for | rinting inks is made from it ; but it is 

 used witli suicidal wastefulness, which causes anxiety, as 

 many wells give out in le.-'S than five years. The report 

 looks to its economic and safe control. For household use, 

 it might otherwise be dangerous, and such usie has com- 

 menced, though no practicable method of deodorising it 

 has been found. Being composed largely (9G per cent.) of 

 marsh gas, its value as a heating agent is high, and its 

 density is about half that of air. One pound (23.5 culnc 

 feet) of g-is has a theoretical evaporating ))Ower of 241b. 

 of water, 20 lb. having been actually evaporated. The best 

 method of burning it is not generally known ; experiments 

 with injector burners show that they do not suck in suffi- 

 cient air for complete combustion, and the best results have 

 been from numerous jets in contact with the whole heating 

 surface of the boiler. Tlie value of the gas, as compared 

 by evaporation tests with coal at §1.40 per ton, is only 

 Scents per thousand feet (which suggests tliat even our 

 ordinary gas companies make profits), but its use is im- 

 mensely more convenient ; no stacks are needed, and tlie 

 furnace reduces to a simple nonconducting chamber. The 

 gas has just been turned on to the city waterworks. On 

 the first day's excursion numerous furnaces were seen 

 running with gas blown in through rough, J. in. nozzles ; 

 and two or three lines of 5-iu. pipe lay on the surface of the 

 railway embankment. 



A gas well has lately been opened within the city 

 limits, at a depth of 1,G00 feet, on the property of Mr. 

 Westinahouse. 



THE 



TAEANTULA OF SOUTHERN 

 CALIFORNIA. 



UGLY, vicious, energetic, and to a certain degree 

 poisonous, are the spiders that infest the southern 

 part of California, and yet when closely studied they pre- 

 sent many jieculiar characteristics, both in regard to their 

 structure and habits. Among the most valued trophies 

 tourists carry away with them from the coast are neat cards 

 adorned with these animals, and a case containing the nest 

 so arranged as to show its wonderful trap-door and the 

 delicate lining of the interior. The adobe ranches are full 

 of these strange little hahitations, and some of the .sunny 

 valleys among the foot hills are literally strewn with the 

 small tunnel.", capped with the almost invisible door. Our 

 engraving shows the tarantula (Mi/gale hentzii) as he is 

 about to enter his abode, both being full size. 



The general appearance of the tarantula is very clearly 

 shown in the engraving. The legs are larger, and are not 

 furnished with so long and dense a growth of hair as are 

 the specimens found in other sections of the south-western 

 States. The back is covered very thickly with extremely 

 tine short hair ; the back and the outer joints of the legs 

 are of a liiiht brown colour, the remainder being of a 

 deeper shade. The forward part of the head is divided, 

 and each division terminates in a sharp, downwardly 

 curved, and jt-t black horn or hook. 



The tarantula pi>unces upon his prey, and thrusting in 

 the hooks most securely holds his victim. It is seldom met 

 in the daytime, preferring to seek its food during the 

 n ght, returning to its nest in the early morning. Although 

 pugnacious when cornernd, he will not seek a tight, and is 

 more anxious to escape than the stranger whom he chances 

 to meet. 



This tarantula is justly celebrated for the architectural 

 skill he di-ptays and for the luxurious comfort of his 

 dwelling Having selected a suitable site, he digs a hole 

 varying from four to eighteen inches in depth, and just 



large enough around to admit him easily, although it in 

 puzzling to conceive how he ever gets his long, ungainlj', 

 and many-jointed legs comfortably disposed in so small a 

 space. 



The walls are carefully smoothed, and are completely 

 covered with an exceedingly fine faVjric of his own manu- 

 facture. The top of this tunnel is slightly tiared, and in 

 this widened part is fitted the door, which is hinged at one 

 side so that it may be easily lifted. The inside of the door 

 is finely finished, and covered with a web similar to that 

 on the side. The tarantula knows that this door is not 

 heavy enough to ensure a light fit when it is dropped, 

 so he makes a small handle near tlie centre of the 

 under side by which he pulls the door closely 

 down, thereby insuring a joint that most efiectually 

 excludes all dampness from his abode. The handle is a 

 strong web, the two ends of which are attached to the 

 door at points about one-sixteeuth of an inch apart. The 

 outside of the door is placed about at the level of the 

 ground, and is so nearly the eame colour as the surrounding 



soil that it can be discovered only after the most careful 

 search. The joint of the door is so well made and the 

 colours are so nearly alike that it is almost impossible to 

 ascertain upon which side the hinge is placed, except by 

 raising the door. The framing of the door seems to be a 

 coarse, stronir web, which is extended at one side to form 

 the hinge, and which is bonded with earth to give it the 

 requisite stiffness. The hinge is about three eighths of an 

 inch wide, and acts as a spring to shut the door immediately 

 alter the owner's exit. For the tarantula and nest from 

 which our engraving was made, we are indebted to the 

 courtesy of Mr. H. J. Finger, of Santa Barbara, Cal. — 

 Scient'Jic American. 



Remedy for Toothache. — Melt two parts of spermaceti or war 

 and dissolve in it two parts of chloral hydrate and one part of carbolic 

 acid. Dip pieces of cotton into the mixture and let it cool. For 

 use, detach a small quantity, soften it with a gentle heat, and press 

 It into the hollow tooth. — Rundscli. f. Pharm, 



