SCIENCE— SUPPLEMENT 



small quantities of aluuiinum deoxidize the melt 

 and prevent atmospherie corrosion of the casting. 

 In the electrodeposition of metals small quantities 

 of ' addition compounds ' -(vliich are in many eases 

 protective colloids, give a desirable eathodie de- 

 posit. Auer von Welsbach found the great effect 

 produced by eeria in the thoria mantle, the opti- 

 mum value being aibout 1 per cent. Thus in a 

 certain flame a pure thoria mantle gives 7 candle 

 power, whereas the standard mantle with 1 per 

 cent, ceria gives 88 candle power. With y^ per 

 cent, ceria the luminosity sinks to 56 candle 

 power, while with 5 per cent, ceria it is only 44 

 candle power. Goodyear had no trou:ble in vul- 

 canizing his rubber because of the various nitro- 

 genous impunities present in the crude product of 

 hds day. With the advent of modern pure plan- 

 tation rubber, it has become necessary to add 

 various accelerators. Old patents show that cellu- 

 loid dissolved in the ' ' wood spirits ' ' of tiliat day, 

 which contained ketones in considerable quantity, 

 but refined wood alcohol is not a solvent for it. 

 Traces of lead tetra-ethyl will take the 'gasoline 

 knock' out of an internal combustion engine, even 

 0.06 per cent, being effective. ' ' 



But other traces hinder rather than help, Mr. 

 Alexander said. Iron was described as powerful 

 in small amounts. A m'anufacturer of brewing 

 sugar came to see how his new product was work- 

 ing in a brewery and found the brew-master run- 

 ning an inky black liquid into the sewer, he re- 

 lated. Being a diemist, he immediately wired his 

 analytical department that their product was full 

 of iron, and in reply received a telegram saying 

 that the batch complained of had only 0.002 per 

 cent, of iron. But that was enough to make 

 plenty of ink with the hop tannins. 



"In making dry baitteries, traces of iron in the 

 pyrolusite or of copper in the ammonium chloride 

 are highly objectionable," he said, giving further 

 examples. ' ' One part of sulfur per milUou in 

 coooanut oil is said to create trouble in the soap 

 making process. In lead burning traces of arsenic 

 in the hydrogen used to make it impossible to 

 secure a good joint. Attempts to make a good 

 nickel steel were for years frustrated by impuri- 

 ties present in the commercial nickel of the day. ' ' 



PLAGUE RATS MENACE HAWAII; BUT 

 POISON CAKES COMBAT THEM 



Science Service 

 Lives and fortunes are the stake in a tre- 

 mendous war against field rats now being con- 

 ducted by the territorial board of health and the 

 sugar plantations of the Hawaiian Islands. The 



results of this war are likely to be of assistance 

 throughout the world in campaigns against the 

 rat, one of tlie worst enemies of mankind. 



It is stated by those who have studied the prolb- 

 lem at the experiment station of the Hawaiian 

 Sugar Planters' Assoaiation that the common 

 field rat destroys sugar cane on these islands 

 valued at $100,000 each year, and probably the 

 damage is in excess of this sum. 



Worse than this huge tax on the industry, how- 

 ever, is the ever present danger of bubonic plague 

 from infected rats. Twelve deaths among Jap- 

 anese and Filipino plantation laborers occurred 

 within the past few months on the Hamakua coast, 

 island of HawaiL 



A new and successful method for wholesale kill- 

 ing of rats has just been discovered. Poison rat- 

 cakes are being manufacituired by the millions at 

 Honokaa plantation and are spread broadcast 

 through more than ten thousand acres of cane 

 fields and waste areas, resulting in the death of 

 so many rats that where the board of health pre- 

 Aliously trapped over two thousand rats a month, 

 it now catches only about fifty. 



The poison used is barium carbonate, deadly to 

 rats and field mice, but only slightly poisonous 

 to human beings, livestock and poultry. The 

 poison is mixed with flour dough and made into 

 small round cakes less tham. an inch in diameter 

 and about one fourth inch thick. 



A new and very important feature, for which 

 patents have been applied, is the coating of pax- 

 af&ne lOver the cakes to protect them, from damp- 

 ness and moulding, thus insuring their effective- 

 ness for many months. A very small nibble at 

 one of these poison cakes vdll kill a mouse, while 

 a piece as large as a small pea will kill a rat. 

 Honokaa Sugar Company is manufacturing these 

 rat-cakes chiefly for its own use, but it is also 

 selling some at nominal cost for trial use on other 

 plantations. 



A man on horseback, dropping a rat-cake about 

 every ten feet, can cover aji area of 35 acres in 

 one day, at a total cost of sixteen cents per acre. 

 This done two or three times a year is sufiicient 

 to control thoroughly this very serious pest. 



Other poisons have been tried at Honokaa. The 

 best of these is strychnine wheat placed in small 

 bamboo tubes and wrapped with parafSne paper. 

 The usual methods of podsondng are intended for 

 ujse on a small scale and no effective system has 

 been evolved previously which is cheap enough to 

 use over large areas and impei"vious to the 

 weather. 



Many efforts were made along other lines before 



