September 21, 1S83.] 



SCIENCE. 



407 



would now aflbrd their entomologist, Miss 

 Ornierod, an opportunity for directing a scries 

 of comparative experiments to test the truth 

 of these beliefs. 



The report is well illustrated, partially hj- 

 some of tlie well-known figures of Curtis, and 

 partially by original figures drawn by the 

 authoress. 



WEEKLY SUMMARY OF THE PROGRESS OF SCIENCE. 



MATHEMATICS. 



The elliptic differential equation. — 51. Rud. 



Sturm h.i.s here given a method of integration for the 



ilx fty _ n 

 general elliptic differential equation — p-= ± y- — 0, 



where X and F are quartic functions of x and y re- 

 spectively, say, X = E{x — a) {x — b) (x — c) (x — d), 

 and Y a similar function of y. He shows that this 

 equation can be integrated directly by aid of an 

 integrating factor which he determines. Denoting 

 by Xoo . . . Yab ■ ■ . the products of two of the 

 factors X — a, X — b . . ., y — a,y — b . . . , then 



the left-hand side of the equation -p= ± -7^ = is 



VX Vi" 



made the exact differential of 



by multiplying it by the quantity 



..fiu 



(Y^r^; JIHj; + y)(a + b)-xy- ab]^Scjyab 



T VAx + y) {c + d)—xy - ( d]<i/S^Frd] • 

 — {Math, mm., xxl] t. c. [238 



PHYSICS. 

 Electricity. 



Efficiency of telephones. — K. Vierordt meas- 

 ures the weakening of sound through telephones by 

 diminishing the sound at the tr.ansmitter until it 

 just becomes inauilible at the other end. The sound 

 is measured by the mass and height of a small 

 leaden sphere, which is dropped upon a tin plate. 

 Using two Siemens-Hal!-ke telephones, of 20'> and 

 208 S. U. resistance respectively, he found that the 

 loss over thirty-four m. of wire was less than seventy- 

 five per cent of the loss iu air. — (.-Inn. pkys. chem., 

 .\ix. lid".) J. T. [239 



Electric lighting. — Ganz & Co. of Budapesth 

 find, that, with a continuous current, the carbon 

 filament of an incandescent lamp gives out first at 

 the end where the positive current enters, a spot of 

 carbon being deposited on the neighboring part of 

 the glass. If alternating m.ichines are used, the life 

 of the lamp is almost exactly doubled, and when the 

 deposit forms it is all around the case. — (Emjinefr- 

 {»£/, June 15.) J. T. [240 



ENGINEERING. 

 A great 'Sound steamer.' — The steamer Pil- 

 grim, of the Old Colony steamship company, was re- 

 cently added to the fleet now plying through Loug 



Island Sound. The vessel is the largest and the 

 must expensively fitted up of all steamers which have 

 yet been built for those waters. The hull is of iron, 

 d(mble, and built in compartments. The boiler space 

 is so enclosed by iron bulkheads that the danger of 

 fire is wholly avoided. The engines are of the stand- 

 ard beam-engine type, and fitted with the Stevens 

 valve-gear. They were designed by Messrs. Fletcher 

 & Harrison, and built by Messrs. Jolin Roach & 

 Son. The steering is done by means of a Sickles 

 steam steering gear, and the lighting is performed by 

 Edison dynamos. The hull is 390 feet long on deck, 

 375 on the load line; the beam is 50 feet over the hull 

 and 87.6 feet over the 'guards;' the depth of hold 

 is 18.0 feet; draught of water, 11 feet. The engine 

 has a steam-cylinder 110 inches in diameter and 14 

 feet stroke of piston. There are 12 boilers of steel, 

 an<l calculated for a pressure of .50 pounds per square 

 inch. The total power is estimated at 5,.500-liorse 

 power. The wheels are of the radial type, and are 41 

 feet in diameter, weighing 85 tons each. The shafts 

 are 26 Inches in diameter. The cylinder weighs 30 

 tons; the bed-plate, 30 tons; the beam, 33 tons; the 

 condenser, 60 tons. The machinery will weigh, alto- 

 gether, with wat^r in the boilers, l,.3u5 tons. There 

 are 103 water-tight compartments; and it is consid- 

 ered that it will be impossible to sink the vessel by 

 collision or grounding. There are 912 electric lamps 

 operated by two Edison dynamos of a total of 11,400- 

 candle power. They are driven by an Armington & 

 Sims engine, built at Providence, of 150-horse power. 

 The grand saloon is the largest in the world : it is 350 

 feet long, and acconnuodates 1,400 passengers, for 

 whom stale-rooms are provided. — (Sc. Ainer., June 

 30.) R. H. T. [241 



CHEMISTRY. 

 (Gftirrr,!. phijsUid. and inorganic.) 



Apatites containing iodine. — In continuing the 

 study of the formation of artificial apatite*, A. Ditte 

 fused baric iodide with a mixture of sodic iodide and 

 amnionic phosphate, the latter in small quantity. On 

 slow cooling, the mass crystallized in hexagonal prisms 

 of the composition Bal... . 3Bai(PO,),. When am- 

 monio arseniate was substituted for the phosphate, the 

 corresponding iodarscniatp, 15al, . 3 I5a.,( AsOj,, was 

 formed. The iodvanadate, Bal^ . 3 Ba,(VO,)j, crys- 

 tallized in transparent prisms. The strontium com- 

 poimds, Sri, . 3Sr;,(POJj, and Sri, . 3Sr,(AsO,)4, 

 and calcic iodvanadate, Calj . 3Ca,(V04)i, were ob- 

 tained. — ( Comptcx rendus, xcvi. 1220. ) c. F. M. [242 



The spectrum of beryllium. — Mr. H. N. Had- 

 ley finds that the spectrum of beryllium .shows no 

 marked analogy with the spectrum of calcium, mag- 



