SCIENCE. 



*5.80 



Science, made to follow one another in immediate and rapid 

 Curiosities succession. 



' n * In order to prove the power of his gi* n t Mr. irer- 



N ""V'' kins has constructed 



Science, 



Curiosities 



in. 



the complement of the dip, s determined by an ex- 



Perkins's 

 steam 

 rocket. 

 Fig. 14. 



Fig. 15. 



the rate of 240 ,n a 



and with 



one side amf squeezed out. The original size of the 

 bullets were 0.65 of an inch, but after striking the tar- 

 get, they were plano-convex, their diameter being 

 1.070 inches, and their thickness 0.29 of an inch. 



When the gun is constructed for use, the balls are 

 put into a sort of hopper, and the moment one of them 

 falls into its place, a cock is turned, which allows a 

 portion of the highly heated water to flash off into 

 steam, and to propel the ball with a tremendous force. 

 Under our article STEAM, we may, perhaps, be able to 

 give some farther information concerning this curious 

 invention. 



2. Perkins's Steam Rocket. 



This very ingenious invention, which Mr. Perkins 

 has recently secured by a patent, is shown in sec- 

 tion in Plate CCCCLXXXV. Fig. 14. where a b 

 is the rocket or hollow vessel made of wrought iron. 

 A piece of iron b is screwed into the end of it, and 

 having a small aperture or bore through it. To the 



j i 1.1 . ! {+ \ 1 _ A ' 



viation of the needle placed at any point 



of the sphere, was represented by the following formula. 



Tang. A=A Sin. 2 x Cos. I. 



A being the latitude, and / the longitude of the needle, 

 or that the ttnurent of the deviation is proportional to 

 the rectangle of Ihe sine of the double latitude, and the 

 cosine of the longitude. 



By making the experiment at different distances, he 

 found that the tangents of the angles of deviation were 

 reciprocally proportional to the cubes of the distance, 

 and using balls of different sizes, that the tangents of 

 the angles of deviation were proportional to the cubes of 

 the diameters. Hence he deduced the following general 

 formula for the deviation. 



A=A 



in which A is the angle of deviation, D the diameter 

 of the ball, d, the distance of the needle, I the longi- 

 tude of position, A the latitude, and A a constant fac- 

 tor to be determined by experiment. 



The most important and the most useful of Mr. 



piece a is attached the tail of the rocket, in the guide Barlow's discoveries, is, that the attracting power of 

 rods c, c, in place of the usual rocket stick. The hoi- j ron bodies for the magnet resides wholly on their sur- 

 low part of the rocket a b is then to be nearly filled f ace) anf j[ j s independent of their mass, provided the 



1.1 1 t f* * 7"*._1.. A *^* .1 x-vrt.l /*_ 



with water, and the bore in the piece of iron b is to be 

 filled up with a plug of brass, which will confine the 

 water within under a very high pressure. 



Thus prepared the rocket is now placed in a fur- 

 nace, shown in Fig. 15. in which is built a cylinder 

 dd of cast iron, open at both ends, and lying oblique- 

 ly. The rocket being put into the cylinder, and the 

 heat applied below, the rocket is heated to such a de- 

 gree as to melt the brass plug, when the water escapes 

 in the form of steam with tremendous force, and 



thickness exceed about the 20th part of an inch. 

 Hence it followed, that hollow balls or shells, whose 

 thickness exceeded the 20th part of an inch, had the 

 same power as a ball of solid iron of the same size, a 

 result which was confirmed by direct experiment. 



To these curious deductions of Mr. Barlow, we 

 shall add the following conclusions, deduced by M. 

 Poisson, from his equations of magnetic equilibrium. 



1. That though the boreal and austral fluids are 

 distributed throughout the mass of a body magnetised 



drives the rocket forward in the direction of the cy- by induction, yet the attractions and repulsions which 



linder. By employing plugs of different metals, or 

 of such alloys as melt at given temperatures, the force 

 with which the rocket is propelled is completely un- 

 der the control of the operator. This most ingenious 

 invention is obviously applicable to the projection of 

 all kinds of projectiles, such as shells, &c. See New- 

 ton's Journal oj the Arts, vol. x. p. 48. 



MAGNETISM. 



Since our article MAGNETISM was published, many 

 curious discoveries have been made in that science ; 

 but the limits as well as the nature of this article will 

 only permit us to notice the most popular. 



1. On the Magnetism of Balls and Shells rf Iron. 



On the Although it has been long known that a bar of iron 



Tb'n" 5 "^ P* acec * vertically or perpendicular to the magnetic 

 shells of equator, has in our latitudes its lower end a north 

 iron. pole, an ^ i* 8 upper end a south pole, yet it was left 



to Mr. Barlow to determine the exact magnetic con- 

 dition induced upon balls and masses of iron by the 



it exercises externally are the same as if it were mere- 

 ly covered by a very thin stratum formed of the two 

 fluids, in equal quantities, and such that their total 

 action upon all the points within them should be equal 

 to nothing. 



2. A magnetic needle placed in the interior of a 

 hollow sphere of soft iron, and so small as not to exert 

 any sensible influence on the sphere, will not be sub- 

 ject to any magnetic action, and will consequently not 

 be subject to any polarity from the effect of the earth/a 

 magnetism, or from that of any other magnet placed 

 without the hollow sphere. 



3. That if magnets are placed within this hollow 

 sphere, their action on a small needle without it, 

 joined to that of the sphere itself, as magnetised by 

 their action, will produce a result equal to zero. 



4. That the interposition of a plate of soft iron of 

 any given thickness, but of a great extent, must be suf- 

 ficient to prevent the transmission of the magnetic 

 action. 



5. That though the magnetism is not confined to 

 the exterior surface of the hollow sphere, and though 



magnetic action of the earth. He found that there its intensity may be determined for any point of the 

 exists in every ball of unmagnetised iron a plane of solid shell, yet the magnitude of the three component 

 no attraction which passes from north to south, and forces produced by it (on a point without it) is 



