November i, 1889.] 



SCIENCE. 



299 



upon the blue ground by using a pen dipped in water. If, how- 

 ever, the paper with its blue markings be exposed to a gentle heat 

 for a few minutes, the blue changes to black, and the characters 

 are then no longer destroyed by water. 



— At the thirty- ninth meeting of the Institute of Electrical En- 

 gineers of this city, on Oct. 29. Mr. George B. Prescott. jun., read 

 an interesting paper on some methods of regulating accumulator 

 batteries in electric lighting. The paper was well illustrated by 

 numerous diagrams. 



— There was a preliminary meeting of the International Con- 

 gress on Celestial Photography at Meudon, France, on Sept. 20, to 

 consider the programme that had been drawn up by the provisional 

 committee. A few slight alterations were made in the original 

 scheme, as we learn from Nature, but the details of the work were 

 not entered into. It was, however, decided that the greatest lati- 

 tude should be allowed in the choice of instruments, and that each 

 observer should employ that instrument to which he was accus- 

 tomed, having no regard to uniformity. In order to indicate the 

 spectroscopic work included in the programme, a change in the 

 style of the congress was agreed to. It is henceforth to be the 

 " International Congress on Celestial Photography and Spectros- 

 copy." 



— iVIr. Hannay summarized his new white-lead process at the 

 recent British Association meeting by stating that the lead ore as 

 it comes from the mines is volatilized and oxidized by the air, the 

 fumes are condensed in a slightly acid liquor, and the resulting 

 sludge is washed and dried for the market without having been 

 touched by the men. He does not employ women at all in his 

 Glasgow works. The condensed material is extremely fine, firm, 

 and of great covering power. The volatilization is effected in an 

 ordinary lead-smelting furnace, but here the object is to get as 

 much fume as possible. The advantages of this process are, that 

 the white lead is made in a day instead of the three months of the 

 Dutch process ; that it starts with the ore, and not with the puri- 

 fied metal ; that it is obtained in a fine powder instead of a hard 

 crust, which has to be ground ; and most important of all, as En- 

 gineering points out, that there is hardly any danger for the work- 

 men. Some of these advantages, claimed specially as regards the 

 purity of the product, were, however, questioned by Sir Lowthian 

 Bell, although the process might develop. 



— In the April bulletin of the Hatch Experiment Station of the 

 Massachusetts Agricultural College at Amherst, report was made 

 of the results of heating, during the months of January and Febru- 

 ary, two greenhouses built side by side, of the same size, one by 

 means of steam, and the other by hot water ; the conditions being 

 the same as far as possible, except thai the house heated by hot 

 water was more exposed to the prevailing westerly winds than the 

 other. The results were so marked, and so decidedly in favor of 

 the hot-water system, that the report has provoked many inquiries 

 and some criticism. In order to make their position more fully 

 understood, and to answer some of the questions that have arisen, 

 they make some further explanation of the conditions under which 

 the tests were made, and report the results obtained for the months 

 of March and April. With other boilers and with other conditions, 

 different results may possibly be obtained ; but they know of no. 

 recorded experiments where accurate observations have been made, 

 most of the reports being based upon guess-work or casual ob- 

 servation. The boilers used consist of cast sections, arranged in 

 such a manner over the grate as to form a return flue arrange- 

 ment, the smoke passing off in the front. In the hot-water boiler 

 five sections were used, the area of heating surface exposed to the 

 tire being 74.5 feet. The steam boiler consists of eight sections, 

 the aggregate area exposed to the fire being 61.12 feet below the 

 water-line, and 24 feet above, making the total heating surface of 

 the steam boiler 85.12 feet. Tables are published in the bulletin 

 for October showing the comparative results of the use of the two 

 boilers for the months of March and April, 1889. These tables 

 show that the average temperature of the house heated by hot 

 water was 2.3 degrees higher than that heated by steam, and that 

 the amount of coal consumed was one ton 106 pounds less in 

 the former than in the latter. The total coal consumed by the hot- 

 water boiler from Dec. 23, 1888, to April 24, 1889, was four tons 



1,155 pounds. The average daily temperature for the four months 

 was 53.5°. The total coal consumed by steam boiler from Dec. 

 23, 1888, to April 24, 1889, was 5 tons 1,261 pounds. The aver- 

 age daily temperature for the four months was 51.2°. 



— The strawberry crop in Massachusetts this season, as re- 

 ported by Samuel J. Maynard of the Hatch Experiment Station, 

 Amherst, Mass., has been much smaller than for the past ten 

 years. The causes that have contributed to this failure are in part 

 the cold, wet summer of 1888, which promoted a late growth, in 

 which the fruit-buds were not matured sufficiently to withstand the 

 winter; the long, open winter, in which the plants were not well 

 protected, and the continued wet weather of the past spring, pre- 

 venting perfect fertilization. Few, if any, of the new varieties have 

 shown qualities which make them superior to those already in gen- 

 eral cultivation. The tendency of the market has been to demand 

 large berries at the expense of quality. Such berries can only be 

 grown under the highest state of cultivation, which many growers 

 have not yet learned is a necessity to the profitable growth of the 

 strawberry. 



— Mr. Clarence M. Weed, entomologist and botanist of the 

 Ohio Agricultural Experiment Station, summarizes the results of 

 a series of experiments on the prevention of injuries of the potato- 

 rot as follows : (i) that a large proportion of the injury done by 

 the potato-rot can be prevented by spraying the vines with the 

 Bordeaux mixture ; (2) that this treatment apparently diminishes 

 the amount of scab affecting the tubers ; (3) that by adding Lon- 

 don-purple to the mixture the same treatment may be made effec- 

 tive in preventing the injuries both of the rot and Colorado potato- 

 beetle. 



— Extralite, a compund which belongs to the panclastite group 

 of explosives, is very similar to roburite, securite, bellite, romite, 

 etc., and, like them, depends for its action upon a non-explosive 

 combustible agent which becomes explosive by the admixture of 

 an oxidizing agent. It is a mixture of ammonium nitrate, potas- 

 sium chlorate, and naphthalene, and in appearance resembles C 

 sugar as far as color and consistency are concerned. It is claimed 

 for it that it is safe to handle, not liable to spontaneous ignition or 

 accidental explosion (such as may be caused by striking or con- 

 cussion due to falling against hard surfaces, like iron or stone), not 

 liable to freeze, not explosive in ignition by flame, and can only be 

 exploded by percussion-caps and when within rigid enclosure. 

 The latter quality has made its use practicable for shells and other 

 projectiles, but it is chiefly for mining and blasting purposes that it 

 is recommended. In some experiments performed with it on the line 

 of excavation and- blasting for the laying of water-pipes in Central 

 Park, opposite West 97th Street, and described in The Engineering 

 and Mi?iing Journal, its claims were fully demonstrated. A fire 

 was built of wood and paper saturated with kerosene, into which 

 several cartridges were opened, but the preparation only burned 

 away without any evidence of its explosive power. A percussion- 

 cap and fuze were attached to an extralite cartridge, and the fuze 

 lighted. The cap went off, but the cartridge remained intact. 

 Equally futile were all efforts to explode it by pounding it on a 

 rock. Finally three borings in the solid rock were loaded with it. 

 One hole was eighteen inches deep, and eight ounces of the explo- 

 sive were rammed into it. The others were twelve and eight 

 inches respectively, and four ounces were put into them. The 

 charges were connected and fired. The result was perfectly satis- 

 factory, and demonstrated its special power as a rending agent. 

 While dynamite has greater influence, by its very rapid action in 

 pulverizing the surrounding rock, this explosive, although equally 

 as powerful, by its more retarded action expends its force in shat- 

 tering larger weights of rocks. It is claimed for this preparation 

 that its use for blasting purposes in mines is of great value, owing 

 to the fact that no noxious fumes are generated, and that the pow- 

 der is almost smokeless. This statement has been disputed in 

 England by those who have used roburite, although that explosive 

 has received very high recommendations from certain quarters. It 

 is interesting to note that extralite is the first of this class of explo- 

 sives to be manufactured in the United States, and, owing to its 

 general safety, it may prove a formidable rival to the various dyna- 

 mites now on the market. 



