Nov. 2 1, 1889] 



NATURE 



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also no opportunity for the filtering through of small por- 

 tions of dissimilar air, and, if portions do descend into 

 the lower levels, they are broken op, diffused, and dis- 

 persed. Still, in the colder half of the year, if the lower 

 wind blows from between east and north, and does not 

 xtend to a great height, a strong mist may be pro- 

 duced by its being mixed with detached portions of the 

 westerly upper current, which take a long time to be 

 thoroughly incorporated and dissolved, and contain more 

 vapour than they can hold invisible in contact with the 

 cold surface-breeze. Thus the prevalence of much haze 

 with a north-easterly gale indicates an equatorial upper 

 current, and the polar wind is apt to be replaced by it 

 before long. With regard to showery weather, it may 

 almost be said to be the opposite of hazy weather, and for 

 the following reasons : — First, as we have seen above, 

 showers are produced by the upward projection of lower 

 air, containing a good deal of vapour, into upper cold air 

 of the same kind. Then, they are often the expression of 

 a state of the atmosphere when the interchange between' 

 the upper and lower strata proceeds by large ascending 

 columns and large down-rushes, instead of by small con- 

 vection currents, and ascending and descending filaments 

 over a very large area. The clearness of the air with a 

 showery north-east wind is quite surprising, for it is 

 sufficient to banish to a great extent even London smoke. 

 Here, again, the north-east wind prevails to a great 

 height, and the air is homogeneous and rather dry. 

 When a shower or even a cumulus cloud passes over a 

 large town, the smoke is seen to be drawn up in a moving 

 column to the height of the cloud. Probably the chief 

 cause of the clearness of a showery north-east wind is the 

 prevalence, as in other cases, of the same wind in the 

 upper regions, so that there is no admixture of strange 

 threads in its composition, no strands of extra-humid 

 particles to be rendered visible by incipient condensation. 



(3) Winds between south-west and north. These are, 

 on the whole, clear for a similar reason, for it has 

 been shown that the upper currents in Great Britain 

 usually move from between south-west and north-west. 

 If, as occasionally happens, an east wind blows overhead, 

 they are very far from transparent. 



(4) Fine settled summer weather, with westerly or 

 southerly winds, is clear not only for the reason above 

 stated, but on account of the general moderate dryness 

 of the atmosphere. In such weather, barometric pressure 

 is frequently highest over Spain or France, and our upper 

 currents are accordingly from north-west, becoming 

 warmer as they advance southwards and increasing in 

 capacity for moisture. There would be no condensation 

 if portions of these currents were to descend into the 

 lower air. 



(5) Settled easterly or northerly winds, with either clear 

 sky or high clouds moving from those directions. Haze 

 does not form where the wind is steady, the air dry and 

 homogeneous up to a great height, and equilibrium 

 stable, for there is nothing to lead to condensation except 

 at the particular level of saturation where clouds are 

 manifested. 



(6) Easterly or northerly winds with a high continuous 

 cloud canopy moving in the same direction, small range 

 of temperature, and steady conditions ; or, with detached 

 cumulus in the daytime, and clear nights. The same 

 remarks apply here as to the last. 



(7) North-west wind, reaching that point from west or 

 south, is particularly clear. Great transparency in this 

 case is not a sign of rain, but rather of fair weather. It 

 is probably due to its agreement in general direction 

 with upper currents, the increasing dryness as it reaches 

 warmer latitudes, and to the uniformity and equilibrium 

 attained by passing over the ocean. 



F. A. R. Russell. 



THE PULSION MECHANICAL TELEPHONE. 

 (From a Correspondent.) 



ANEW mechanical telephone of extraordinary power 

 has recently been exciting considerable attention in 

 London and some other cities and towns in this country. 

 It is of American origin, like so many other modern im- 

 provements of exceptional character, being the invention 

 of one Lemuel Mellett, I believe of Boston, U.S. There 

 have been many previous mechanical telephones, as your 

 readers are aware, some of which have obtained much 

 publicity for a short time, and then have been heard of 

 but little more ; but having had opportunities of experi- 

 menting frequently with the new instrument, and observing 

 its vocal power, so to speak, under very various circum- 

 stances, I cannot doubt that it has a great future before it. 



It may be clearly stated at once that the pulsion instru- 

 ment is absolutely independent of all electrical aids or 

 appliances, and therefore needs neither battery power to 

 bring it into play, nor insulation of any of its parts to 

 keep them effective. It consists solely of two cheap and 

 simple instruments connected by an ordinary non-insu- 

 lated wire of copper, or, better still, of a double steel wire, 

 the two parts being slightly intertwisted, say with about 

 a single turn in a couple of feet. The wire (or wires) is 

 simply looped to the instrument at either end, the con- 

 nection being made in a few seconds. The instrument 

 consists of a disk in combination with a series of small 

 spiral springs inclosed in a case of some three or four 

 inches in diameter. These springs, arranged in a manner 

 that has been determined by experiment, and so as to 

 produce harmonized vibrations, appear to possess the 

 power of magnifying or accumulating upon the wire the 

 vibrations which the voice sets up in the disk, and the 

 wire seems to possess — undoubtedly does possess — the 

 power of transmitting to great distances, and giving out 

 upon a second pulsion instrument, the sounds of the 

 voice. 



The ability of this simple system of springs, disks, and 

 wires to convey conversational and other sounds to con- 

 siderable distances with great clearness and distinctness, 

 reproducing the very tones of the voice and the qualities 

 of musical sounds with but little reduction or modifica- 

 tion, is most surprising, and to none more so than to the 

 many men of science who have been recently experiment- 

 ing with it. 



The writer of this notice cannot, perhaps, do better 

 than state his own experiences with this system. After 

 examining and experimenting over several short lengths 

 of wire, some of them exceeding a mile and a half, he 

 last week went to the Finchley Road Station of the Mid- 

 land Railway, from a point near to which a line had been 

 conveyed to near the Welsh Harp Station, a distance of 

 three miles by the line of railway, and of more by the 

 track of the wire, which for the larger part was carried 

 by the telegraph-posts, to which it was attached by very^ 

 simple means. Conversation through this length of line,, 

 of over three miles, was exceedingly easy ; indeed, so- 

 powerfully was the voice transmitted, that an ordinary 

 hat sufficed for all the purposes of the second instrument,, 

 without going near to which conversation was carried on 

 repeatedly by means of the hats of three gentlemen who- 

 were present, the tops of which were merely placed 

 against the telephone wire. 



I then went into the garden of the " Welsh Harp,"' 

 where a short length of wire had been led between two- 

 points, the wire on its way from one point to the other 

 being twice tightly twisted, at an interval of some yards,, 

 round small branches of trees, of about i inch in diameter,, 

 being wound round and round the branch three times in, 

 each case. Strange to say, this tight twisting of the 

 wires round the branches in no way interfered with the 

 transmission of the voice from end to end of the wire. , 



