J 4 Agricultural Gazette of N .8. W , [Jaii. 2, 1920. 



was phosgene. It was used by the British for cylindei- attacks, in projectors 

 and in shells. Phosgene is so deadly that if a fairly low concentration (say, 

 1 in 5,000 to 1 in 10,000) is breathed for about half an hour and the aniuial 

 moves about much, it is ahnost certain to di-op dead suddenly from lO to 12 

 up to 24 hours later. A high concentration causes a spasm in the throat, 

 and the animal dies quickly and suddenly. Gas shells are not worth con- 

 sidering for the purpose of .^exterminating vermin, as their effective use 

 necessitates a target confined to the area shelled and remaining at a low 

 altitude. The four gases principally used in shells were phosgene and 

 diphosgene, chloropicrin, dichlorethyl sulphide, and diphenyl-chlorarsine. 



Phosgene (and diphosgene is similar in its action) has been mentioned. 

 Chloropicrin does not vaporise easily, and, though it is a deadly gas, its 

 action is much slower than phosgene. One of its advantages as a weapon is 

 that it is cumulative in action. It has a faint "chemical" smell. 



Dichlorethyl sulphide (called by the Germans "yellow cross gas") is the 

 " mustard gas " often referred to and is very dangerous to handle. Its not 

 unpleasant smell — like cress or garlic — is very faint, and many men could 

 not smell it at all. The effects from contact with it do not show until about 

 six hours later, and exposure to it leads to blindness for two or three weeks 

 and sore eyes for considerably longer. If the liquid is spilt on the skin, 

 yellow bladdery blisters subsequently develop. Leather satui'ated with oil is 

 a protection from the liquid ; but untreated leather, rubber, and most other 

 materials are quite ineffective. If breathed in high concentrations the inner 

 lining of the lung is destroyed. I f a few pints were spilt in a dugout it was 

 rendered dangerous for four or five weeks, and many men lost their lives 

 through sleeping in such dugouts, being unable to detect the presence of 

 the gas. 



Diphenyl-chlorarsine (or diphenyl-cyanarsine, which is quicker in its action) 

 was called by the Germans " blue cross gas." It was in the form of a solid, 

 contained in a strong glass bottle which was broken and its contents atomised 

 by the explosion of the shell. The gas is as deadly as phosgene, and is com- 

 posed of such fine particles that in a dense cloud of it protection from it is 

 difficult. If it could be projected as a dense smoke it would be an effective 

 weapon against the flying fox, but the operation would necessitate the use of 

 a special respirator. The cloud would be dangerous 3,000 to 4,000 yards 

 down-wind (or, say, 2 to 3 miles), and low-lying pools of water would be 



contaminated. 



Use of Gases for Killing Rabbits. 



In considering the use of these gases for the purpose of killing rabbits, the 

 cloud method may be dismissed as impracticable. Even on a dull, still day, 

 sufficient gas to be fatal would not enter the burrows. Other application, 

 however, might be successful. The gas (say phosgene) could be introduced 

 into the burrows from a cylinder by means of pipes, which could be made of 

 such a size that they could be handled by one man. Careful and well-trained 

 men would be essential, otherwise casualties would occur. The use of chloro- 

 picrin to contaminate open burrows would be scarcely feasible, as its chemical 



