464 



NATURE 



[March 17, 1S92 



periment on surface tension. A drop of water hanging from 

 the end of a vertical glass tube is regulated in size until it is just 

 on the point of falling away from the tube. On dipping the end 

 of a penholder in ether, and bringing the wet end within a few 

 millimetres from the drop, the latter promptly falls. The drops 

 may be produced and adjusted in the following manner : — 



A piece of glass tube, about 8 cms. long and '8 cms. in dia- 

 meter, is made into a pipette with an orifice about '15 cms. 

 diametei-, and fitted with a small india-rubber ball at the other 

 end. The tube is then passed through a hole in a piece of 

 wood large enough to rest on the top of a common tripod 

 stand, as shown in the figure. A strip of wood, or a paper- 



H 



knife, about 30 cms. long, is placed with its centre resting on 

 the top of the ball, one end (a) being held between the two 

 uppermost of a pile of books, and the other end (b) passing 

 under a screw (s). The ball is squeezed, a beaker of water 

 brought under the end of the pipette, and the tube allowed to 

 fill by the expansion of the rubber. By working the screw s, a 

 drop is formed at the end of the tube, and since one complete 

 turn of the screw I use only lowers the end of the rod (b) ^j, inch, 

 it is possible to adjust the drop with great nicety. As the ether 

 is brought up, the absorption of its vapour diminishes the sur- 

 face tension over a small area of the drop of water, and currents, 

 made visible by suspended dust, appear to pass from the interior 

 towards the weakened spot. Bringing the ether still nearer, the 

 drop often becomes much agitated, and finally, when the dis- 

 tance is reduced to about 4 mm., it falls away from the tube. 



E. D. Fridlander. 

 Mason College, Birmingham, February 29. 



The Orientation of Ancient Monuments. 



The deeply interesting results obtained by Mr. Norman 

 Lockyer with regard to the orientation of Egyptian temples, and 

 by Mr. F. C. Penrose with regard to the Greek, tempt me to 

 call attention to an extract from the Century Magazine, May 

 1883, from an article by Frank Gushing, describing a visit to the 

 Zunis, a typical tribe of the Pueblo Indians of New Mexico, in 

 1879:- 



" Each morning just at dawn, the Sun priest, followed by 

 the master priest of the Bow, went along the eastern trail to 

 the ruined city of Ma-tsa-ki by the river side, where, awaited at a 

 distance by his companion, he slowly approached a square open 

 tower, and seated himself just inside upon a rude ancient stone 

 chair, and before a pillar sculptured with the face of the sun — the 

 sacred hand — the morning star and the new moon. There he 

 awaited, with prayer and sacred song, the rising of the sun. 

 Not many such pilgrimages are made ere the ' suns look at 

 each other,' and the shadows of the solar monolith, the monu- 

 ment of Thunder Mountain, and the pillar of the Gardens of 

 Zuni lie along the same trail ; then the priest bless^es, thanks, 

 and exhorts his father, while the warrior guardian responds as he 

 cuts the last notch in his pine-wood calendar, and both hasten 

 back to call from the house-tops the glad tidings of the return of 

 spring. Nor may the Sun priest err ip his watch of Time's 

 flight ; for many are the houses in Zuiii with scores on their walls 

 or ancient plates embedded therein, while opposite a convenient 

 window or small port-hole lets in the light of the rising sun, 

 which shines but two mornings of the 365 on the same place. 

 Wonderfully reliable and ingenious are these rude systems of 

 orientation, by which the religion, the labours, and even the 

 pastimes of the Zuiiis are regulated." 



In like manner, we read in Prescott that at Quito the festival 

 of the Sun-god was held when " he sat upon the pillar," i.e. a 

 pillar cast no shadow. 



Might not this ZuRi ceremonial be a description of one enacted 

 at some primitive astronomical temple such as Stonehenge? 

 and do we not gain the best insight into the minds of those who 

 in the Archaic period first orientated — the Babylonian and 

 Assyrian ziggurats, the pyramids and temples of Egypt, the 

 temples of Greece, and our own Stonehenge— by seeing how a 

 people in a similar stage of intellectual and scientific develop- 

 ment are acting today ? Fred, F. Grensted. 



Merchant Taylors' School, Crosby. 



The Nickel Heat Engine. 



Mr. Karamate, in a letter which appears in your issue of 

 March 3 (p. 416), alludes to a new form of heat engine described 

 by me in your issue of January 28 (p. 294). He states that my 

 device is similar to one by Prof. Stefan. I wish to point out 

 that the two heat engines are quite different in design. The 

 engine of Prof. Stefan has a step by step action ; that described 

 by me is under certain conditions absolutely continuous in its 

 action. The contrast is shown by Mr. Karamate's description 

 of Prof. Stefan's engine ; he writes : — " Nickel plates were fixed 

 on a wheel, like that of a water-mill, and a magnet was placed 

 before it. By heating a nickel plate before the magnet, it was 

 repulsed by the magnet, and a succeeding plate was attracted, 

 so that the wheel commenced to rotate." From this it seems 

 clear that the action of the machine must be step by step, since 

 the different pieces of nickel must come successively under the 

 influence of the magnet and the flame. In my disk form of 

 engine, the action, when the disk has a certain thickness, is cori- 

 tinuous. Mr. Croft has recently shown that when the disk is 

 not so thick as mine was the disk starts in one direction, then 

 stops, and sets off in the opposite direction. It will also be 

 noticed that the distribution of the magnetic field due to two 

 poles is entirely different from that in the machine of Prof. 

 Stefan. Mr. Karamate writes : " By heating a nickel plate 

 before the magnet, it was repulsed by the magnet." I hardly 

 see how this repulsion takes place. Faraday, writing about the 

 behaviour of nickel, states ("Experimental Researches," vol. iii., 

 2346) ; " Upon being heated the nickel soon became indifferent 

 to ordinary magnets, but, however high the temperature, still it 

 pointed to and was attracted by the electro-magnet." Surely 

 the action of the engine is due to one piece of nickel becoming 

 partly non-magnetic owing to a rise of temperature, thus up- 

 setting equilibrium, and allowing the next piece of nickel to 

 approach the magnet and consequently the flame. 



I may add that E. Berliner in 1885, and Edison in 1887,. 

 patented magnetic heat machines on the step by step principle. 

 Frederick J. Smith. 



Trinity College, Oxford, March 4. 



The Limpet's Power of Adhesion. 



I WOULD like to call the attention of your readers to the 

 results of some experiments, which, I think, are original, re- 

 ferring to the power of adhesion of the common limpet (^Patella 

 vulgata). 



The experiments were carried out as follows, with the assist- 

 ance of my friend J. Sinel, of the Biological Laboratory here. 

 The shell of the limpet in situ was perforated, so as to allow of 

 the attachment of a delicate spring balance, by means of which 

 a gradually increasing strain could be put upon the animal, in a 

 direction normal to the foot. The pull was increased until the 

 animal became detached, and the final weight and the greatest 

 and least diameters of both foot and shell noted. 



The following figures are compiled from a series of twenty 

 consecutive experiments, and are typical of other similar series. 

 The individuals operated on were not chosen in any way. 

 Avcra<res of Twenty Consecutive Experiments. 



Area of shell, in square inches ... • i'07 



Pressure per square inch of shell 22 '5 pounds. 



Area of foot, in square inches ... ... ... '45 



Pressure per square inch of foot 54'3 pounds. 



Gross weight 23-9 ,, 



Maximum pressure per square inch of shell area 31 '3 ,, 



Minimum ,, ,, ,, ,, 13 '9 >» 



Maximum ,, ,, ,, foot area 71-1 „ 



Minimum ,, ,, ,, ,, 37'i >• 



Maximum gross weight ... ... ... ... 32 ,, 



Minimum ,, ,, ... 12 ,, 



NO. I 168. VOL. 45] 



