SCIENCE. 



S95 



rce, 

 ("uriOklttO* 



for measuring the real magnitude of the compartment 

 in the pavement, and they accordingly increased in 

 size, diminishing again when the person had patted 

 s1 "V""*' from our view. Edin. Jour, of Science, No. VII. p. 90. 



17. Mr. Ritchie t Improvement on the Phanlatmagoriu. 



Mr. Kit- In our article OPTICS, Vol. XV. p. Mo, we have al- 



ready described the phantasmagoria. The following 

 improvement upon it has been proposed by Mr. Ritchie 



phantat. of Tain. 



" In the common phantasmagoria," says Mr. Ritchie, 

 " the object becomes brighter and brighter as it dimi- 

 nishes, or as it seems to retire, till it verges into a lu- 

 minous point. Now this is so completely contrary to 

 what takes place in nature, that the momentary belief 

 of reality, EO forcibly impressed on the mind, becomes 

 gradually weakened, and at last totally vanishes. To 

 supply this defect, I would therefore propose the follow- 

 ing alteration, which will render the deception more 

 natural and striking. Let a small portable gasometer 

 be procured, capable of holding a sufficient quantity of 

 condensed oil gas. Let a stop cock, having a small 

 groove, gradually deepening, be adapted to it, so that 

 the quantity of gas escaping to the burner may be in- 

 creased or diminished at pleasure. By diminishing the 

 light according to a certain law, the brilliancy of the 

 object will be gradually improved as it retires, the linea- 

 ments of the figure will become shadowy and obscure, 

 and the phantom itself will at length vanish into thin 

 air.' 1 See The Edinburgh Journal of Science, No. vii. 

 p. 37. 



PNEUMATICS. 



1. Detcription of the Common Air Gun. 



Description Th e a ; r g un o f the ordinary construction consists of 



of the com- two brasg barrels, viz. of an inner barrel A, Fig. i>0. 

 gun." P . late CCCCLXXXVI. from which the bullets are 



Pi ATE discharged, and a larger barrel ECDR on the outside 



CCCCLXXXVI. of the former, for containing the compressed air. A 

 Fig. 2(. syringe SMNP is fixed in the butt end of the gun, 



which, by means of its piston, barrel and valves, con- 

 denses the air through a valve EP, in the outer bar- 

 rel ECDR. The ball K is rammed down into the 

 barrel A in the usual manner, and when the trigger 

 O is pulled it opens a valve at SL, which allows the 

 compressed air to escape, and press with all its force 

 against the bullet, so as to discharge it with immense 

 velocity. By continuing to press upon the trigger, 

 the whole charge of condensed air may be let off at 

 once, so as to impell the ball with the greatest force 

 which the gun is capable of furnishing ; but if it is 

 pulled quickly, and allowed to return, several bullets 

 may be discharged by one condensation. 



Improved An air gun on an improved construction is shown 



air gun. j n pjg 2 1. where A is the barrel, resembling that of a 



'*' * common gun, and c a hollow copper vessel, perfectly 



air tight, screwed to a steel tube b, having a moveable 

 pin in the inside, which is pushed aside by the action 

 of the lock and the pulling of the trigger. The cop- 

 per ball c is charged by means of the condensing 

 Fig. 22. syringe B, Fig. 22. and then screwed on to the tube 



b. The ball being put into the barrel A, and the 

 trigger a pulled, the valve will open, and the whole 

 of the condensed air will rush out, and impell the ball 

 with great force. The charge of air in the vessel is suf- 

 ficient for 15 or H> discharges. 



In the inside of the copper ball is a valve and 

 spring which permits air to enter the ball, but which O|II *J 

 closet tightly by the pressure of the air when it at- 

 ti in i its to escape. The copper ball it screwed tightly 

 to the top of the syringe at b. The handles' 111! are 

 fixed to the barrel B of the syringe, and by pulling 

 them up and down the air is condensed in the ball. 



The magazine air gun, invented by M. Colbe, is re- 

 presented in Figs. '.':{, 24, and --'.5. The object which irgun. 

 the artist had in view was to discharge in succession Hf** ** 

 ten bullets lodged in a cavity. In the representation **' ** 

 of the air gun in Fig. 23. 'the stock is cut off at the 

 extremity of the condensing syringe, the valve of which 

 opens into the cavity between the barrels. The shoot- 

 ing barrel KK receives the bullets in succession from 

 the magazine ED, which is closed at D when the 

 bullets are put in. The circle a b c is the key of a 

 cock perforated by a cylindrical tube, having its dia- 

 meter equal to that of the barrel KK. In Fig. 25. 

 this cylindrical tube makes part of the barrel, and the 

 communication between it and the magazine ED is 

 cut off. The axis in which the cock a be turns is a 

 square piece of steel /, in the end of which is put the 

 square hole of the hammer HH, shown in Figs. I 

 and 25. By turning, therefore, the hammer HH, the 

 cylindrical perforation in the cock, which in Fig. 29. 

 coincides with the barrel KK, may be placed in the 

 position i k, Fig. 25. so as to communicate with the ma* 

 gazine ED. If the gun is now held beneath the arm 

 with the face AB of the barrel downwards, and the 

 magazine KD upwards, one of the bullets b next the end 

 k of the cock will fall into the barrel, where it will be 

 detained in the proper position by the small springs 

 sx. By again opening the cock as in Fig. 25. the com- 

 munication between it and the magazine is cut off, 

 and the bullet is ready to be discharged. This is ef- 

 fected by the combination of levers f hown in Fig. 23. 

 which become visible by taking off the lock. When 

 the trigger ZZ, Fig. 23. is pulled by the part within 

 the guard C, its dotted end 7 within the stock raises 

 the end y of the seer r/ a, and by depressing the end 

 a disengages it from the notch near a upon which the 

 powerful spring W\V moves the tumbler T to which 

 the cock is fixed. The end u of the tumbler depresses 

 the end v of the lever, and its other extremity M, 

 raises at the same time the flat end / of the hori- 

 zontal lever Q, which, by its vertical ascent, elevates 

 the pin /> P which rests upon it. This pin pushes up 

 the conical brass, valve V from its conical seat into 

 which it is nicely ground, and admits the condensed 

 air which drives out the bullet. This valve instantly 

 shuts by the action of the long spring NX made of 

 brass, and is again opened in a similar waj to produce 

 subsequent discharges. It has been found that twelve 

 penny weights of air thrown into a ball 33^ inches in 

 diameter will discharge 15 balls. 



Montucla ascribes the invention of the air-gun to Ot- 

 to Guericke, the inventor of the air-pump ; but David 

 Rivant, in his Elcnicns fArtilltrie, ascribes it to M. 

 Marin, a burgher of Lisieux, who presented one to 

 Henry IV. 



2. The Ascending Snake. 



This little toy, depending on the ascent of a current Tbea*wod. 

 of heated air from a fire place, is one of the prettiest ing m*\it 

 pneumatic experiments wnich we have seen, and has 

 the advantage also of illustrating the action of several 



6 



