April 13, 1888.] 



SCIENTIFIC NE\A^S. 



539 



not due to any actual objective rise of temperature of the 

 skin, but is a sensory illusion due to hypersesthesia or 

 exaggerated excitement of the nerves that are specially 

 connected with heat sensations. 



Dr. Goldschneider found that a similar illusion is pro- 

 duced when the skin is in contact with air saturated with 

 moisture, the difference being as much as 10° Fahr. be- 

 tween the sensations derived from fully saturated and 

 semi-saturated air, i.e., fully saturated air appeared to 

 have the same temperature as semi-saturated air that was 

 actually 10 degrees warmer. 



When on the subject of chlorine, I usually showed mj' 

 pupils the experiment of plunging the hand into a jar of 

 this gas. The sensation of heat in this case is verj' 

 striking, and was then attributed |to the chemical activity 

 of the gas, inducing local oxidation of the blood in the 

 capillaries similar to the action of chlorine in bleaching, 

 but this is not the case with the carbonic acid nor with 

 the aqueous vapour, as proved by experiments made by 

 Dr. Goldschneider on the skin when exposed by remov- 

 ing the epidermis. 



It does not appear that he has included the action of 

 in chlorine in his vestigations. I am surprised at this, as 

 there appears to be some connection between the pheno- 

 mena,and the action of the chlorine — judging from my own 

 sensations — is far more energetic than that of the 

 carbonic acid. It may be that the chemical theory is 

 erroneous, and that the chlorine merely stimulates the 

 nerve, endings to produce the sensation of heat without 

 effecting any actual rise of temperature. 



MEASURING DEEP-SEA CURRENTS. 



ON a former occasion* we described apparatus used for 

 deep-sea sounding, and we now give a short account of 

 the means adopted to measure the Gulf Stream currents. 



For these particulars we are indebted to a report made to 

 the United States Coast and Geodetic Survey Depart- 

 ment by Lieutenant Pillsburj', U.S.N., who commanded 

 the steamer Blake. His object was to anchor in the 

 deep water of the Gulf Stream, and to observe the cur- 

 rents from the vessel so anchored. In the first place, 

 therefore, he had to devise a method of anchoring the 

 vessel expeditiously, with certainty, and with safety to 

 the vessel and appliances. It was, moreover, absolutely 



'" Scientific News, Vol. i., First Series, page 133. 



necessary to relieve the sudden strain due to the motion 

 of the vessel on the anchoring cable. To do this a 

 heavy spar or boom s in Fig. i was attached by a goose 

 neck to the pawl-bitt / in the bow, and this boom was 

 held up by a steel wire rope u at an angle of about 45.* 

 The wire rope then passed through a large block v at 

 the mast-head, and thence through another large block on 

 the deck, the same distance abaft the mast that the end of 

 the boom was forward of it. At the end of the wire 

 rope abaft the block was attached an arrangement of 

 rubber buffers, about eight feet long, into which was 

 hooked a powerful purchase. In this way it will be 

 seen that upon any weight coming on the end of the boom 



the strain was transferred by a straight thrust to the 

 pawl-bitt, a straight thrust downwards on the mast, and 

 a pull forward on the rubber buffers. This arrange- 

 ment worked admirably with great strains ; but the 

 pitching of the vessel rendered it necessary to place the 

 rubber accumulator w between the boom s and the 

 point V. After this there was no trouble whatever. 



The instrument devised by Lieutenant Pillsbury to 

 obtain the strength and direction of the currents at any 

 depth is shown in Fig. 2. There is a freely-moving 

 rudder of thin metal a, and attached to this is a set of 

 four metal cones />, placed at the extremities of two arms 



