HA RD WICKE'S SCIENCE- G OS SI P. 



249 



of Diatoms come under such a category ? It is a 

 common thing to hear and read that the appearances 

 of things under the microscope are not always to be 

 taken as strictly true : and doubtless the microscopists 

 of old days owed some of the queer figures they drew 

 to this cause. The changing colours and form of 

 Gonium perforate as above noticed may perhaps serve 

 a useful purpose, if they warn some young microsco- 

 pists to be very particular in the observations they 

 make ; possibly also some older hands might take a 

 hint. 



Wellington, New Zealand. 



GOSSIP ON CURRENT TOPICS. 

 By W. Mattieu Williams, F.R.A.S., F.C.S. 



HUMAN POLARITY — Some years ago a large 

 number of people educated themselves into 

 the belief that they could sleep better with head to 

 north and feet to south, than if lying east and west. 

 This was between 1845 and i860. It appears that 

 this notion has either revived in America, or has not 

 yet died there. A doctor writing in the " St. Louis 

 Globe Democrat," asserts that the notion has its 

 foundation in true scientific facts, and that each 

 human system has its magnetic poles, one positive 

 and one negative, some persons having their positive 

 pole in the head and their negative in their feet, 

 and viceversd. He proceeds to tell us hat, in order 

 that the person sleeping shall be in perfect harmony 

 with the magnetic phenomena of the earth, the head, 

 if it possesses the positive pole, should lie to the 

 south, or if the feet possess the positive pole the 

 head should lie to the north. 



This doctor, like those with whom I discussed the 

 subject at the time above-named, seems to be ac- 

 quainted only with the declination of the magnetic 

 needle, and to know nothing of the dip. If the 

 positive-footed people are to lie in the magnetic 

 meridian, they must, in our British latitudes, lie with 

 heads 18 degrees W. of North, and with heels up- 

 wards at an inclination of 67 degrees from the 

 horizontal line, or within 23 degrees of the perpen- 

 dicular. 



In 1720 the dip amounted to 74° 4 2 '> or within 

 I5j° of the perpendicular, in London. To retain 

 either of these positions, the victim of "perfect 

 harmony with the magnetic phenomena of the earth " 

 would require to be securely tied by the heels, and 

 all the bedding to be tied likewise, to prevent the 

 tobogganing that would otherwise occur at such 

 angles. At two regions of the earth, viz., at the 

 north and south magnetic poles, the victim of 

 magnetic harmony would require to sleep in per- 

 pendicular position, head or feet downwards, according 

 to which pole, and the positive and negative specia- 

 lities of the individual. 



The statement of the learned doctor, who tells us 



that the positive pole of the person draws one way, 

 but the magnetic pole of the earth draws the other 

 way, and forces the blood towards the feet, affects 

 the iron in the system, tones up the nerves, and 

 makes sleep refreshing and invigorating, indicates 

 the necessity of placing the body accurately in order 

 to obtain the full effect. In our latitude the magnetic 

 force, which determines the dip, exceeds that which 

 effects the declination, or, otherwise stated, the down- 

 pull stronger than the north pull. 



Steering Balloons. — Four months ago several 

 newspapers and magazines informed us that Mr. 

 Peter C. Campbell, of No. 455, Fifth Avenue, 

 Brooklyn, had invented and constructed a "novelty 

 air-ship," a long egg-shaped gas-bag with clock-work 

 to move a fan-wheel at one end, and a horizontal 

 screw below to raise or lower the ship. Besides 

 these there were broad flat wings, extending on each 

 side, to guide the balloon by being raised or lowered 

 at any desired angle, and two flat V-shaped screens 

 spread like the tail of a bird attached to the rear, 

 and just forward of the propeller. These to maintain 

 the perpendicular and to steady the whole. All 

 these appliances are attached to a light frame, which 

 tapers to a point forward. A small electric engine is 

 to actuate the clock-work. We are told that a 

 model three feet long sailed about a room successfully. 

 This sailing of the model may appear satisfactory, 

 but I fear that such experiments on such models 

 with clock-work are necessarily fallacious, for two 

 principal reasons. The first is that in a room the 

 air is still, and a small progress — say of five or six 

 miles per hour, makes a great show, while in the 

 open air such a pace would be insufficient to over- 

 come a very moderate breeze. The mean velocity 

 of the wind in our climate is from twelve to fourteen 

 miles per hour at the surface, or nearer to twenty- 

 nine at an elevation of 1000 feet. With such a 

 breeze, such a machine could do no more than effect 

 a slight deviation from its drift with the wind. 



The second fallacy in ordinary models, is that they 

 do not carry the motive-power machinery. Clock- 

 work of course has no such power, it merely receives 

 and transmits it. The clock-work of the model is 

 supplied by winding before the model is started. In 

 practice the machine that does this work must be 

 carried, and this constitutes a serious addition to the 

 demand for increased bulk of the gas bag. 



The best prime mover yet known, is the muscular 

 power of the aeronaut, and my old friend, Com- 

 mander Cheque, who carefully studied this subject 

 and was very sanguine, concluded that with a feather 

 paddle, which is the best machine, about five miles 

 an hour through the air is attainable by our ordinary 

 balloon. It is very doubtful whether the elongated 

 shape usually designed for these " air ships " would 

 afford any advantage in this respect, as every devia- 

 tion from the spherical figure demands greater surface 



