•January 1, 185)5.] 



KNOWLEDGE. 



15 



air — drawn in at the psriphery and disebarged in a straight 

 line almost pairallel to the axis. 



In my large machine I employ two screws, each seventeen 

 feet ten inches in diameter, and with a pitch of sixteen 

 feet. Each screw has two blades and the projected area 

 of all the blades is ninety-four square feet. When the 

 machine is run over the track at the rate of forty miles an 

 hour, the slip of the screws is eighteen miles an hour. If 

 ■we consider the thrust of the screws on the Moy theory, 

 which is fully explained and elaborated in your last issue, 

 we should find that with eighteen miles slip the thrust 

 would be 152-'i.S lbs. according to the formula V- x -005 x 

 A P (\' being the velocity in miles per hour, A the area 

 in square feet, and P the pressure in pounds). This is 

 computed on the basis that the thrust of the screw is equal 

 to the projected area of the screw driven through the air 

 at the velocity of the slip. Therefore, according to Mr. Moy's 

 theory, it would be 18- x -005x94 = 152-28 lbs. I lind 

 that a great many others besides Mr. Moy compute the 

 thrust of the scre^vs on this same basis ; others, however, 

 believe that the whole screw disc, which in my cise is Ave 

 hundred square feet, should be considered. This would 

 give 18- X -005 x 500 - 810 lbs. screw thrust. However, 

 the iictuiil thrust was found to be rather more than two 

 thousand pounds, or 13-1 times as much as Mr. Moy 

 supposes. 



Lord Kelvin, upon learning that I obtained a screw 

 thrust of over two thousand pounds, came to Baldwyn's Park 

 with some of his scientific friends and witnessed a number 

 of my experiments. Without the least trouble I was able 

 to run the engines fast enough to get this enormous 

 amount of screw thrust. L'pon witnessing this, Lord 

 Kelvin frankly said that everything relating to aerial flight 

 was many times more favourable than had been supposed, 

 and that all the formulte would have to be revised. This 

 practical demonstration, however, is only looked upon by 

 Mr. Moy as a " big joke." Evidently the larger the screw 

 thrust, the bigger the joke. 



Mr. Moy says, in his article in the December number of 

 Knowledge, that my machine, like Henson's, has failed 

 because " it slid backwards and injured its tail." In reply 

 to this I would say that I know nothing about Henson's 

 machine, except what I have heard. I believe, however, 

 that he made a design of a very large machine, and then 

 conducted a few experiments with a very small and im- 

 perfectly made apparatus, and that the power of the 

 engines and the thrust of the screw were so small that if 

 the machine had been dropped from a height, its weight 

 acting upon the angle of the planes would have driven the 

 screw backwards, instead of the screws driving the machine 

 forwards ; that is, the screw thrust under the most 

 favourable circumstances, both in his large design and in 

 his small machine, was so small that it would not balance 

 the backward action of the machine caused by its weight 

 acting through the angle of its planes. 



With my machine, however, the planes are placed at an 

 angle of one in eight, and the screw thrust is two thousand 

 pounds. As my machine weighs eight thousand pounds, 

 it will be seen that the backward action due to the angle 

 of the plane would be considerably less than the screw 

 thrust ; consequently, my machine has no tendency to 

 move backwards, but, on the contrary, iAks move forward at 

 a high velocity, and it has never as yet run backwards and 

 broken its tail. But it appears that facts have no influence 

 on Mr. Moy's mind ; if the facts do not correspond to his 

 way of thinking, "bad luck to the facts then." Unlike Mr. 

 Moy, I do not regard my experiments as a dead failure, as 

 I have succeeded in making a machine which has a lifting 

 efiect greater than its total weight. 



Mr. Moy concludes by suggesting that I should go to 

 Salisbury Plain and propel my machine with a rope, 

 instead of with screw propellers. The machine which 

 depends upon a rope, and is secured to the earth by a rope, 

 would in no sense be a flying machine ; moreover, at the 

 present time I am able to obtain a screw thrust of over 

 two thousand pounds, and I find this quite sutficient to 

 propel my machine through the air ; in fact, if I cannot 

 make a machine which will fly with a screw thrust of two 

 thousand pounds, I think I had better abandon the whole 

 thing. Iq my early experiments with a small apparatus I 

 succeeded in lifting as much as fourteen times my screw 

 thrust, but this was only computing the power actually 

 required for driving the plane through the air. At the 

 time of planning my large machine I expected to be 

 able to obtain a screw thrust of fifteen hundred pounds, 

 and to carry as much as ten times the screw thrust.. 

 When, however, my machine was completed, I found 

 that I could obtain a screw thrust of over two thousand 

 one hundred pounds, but that 1 was uaable to lift ten 

 times the thrust, on account of the great number of tubes 

 and wires which were necessary to hold the engines and 

 the aeroplanes in position, and to give the necessary rigidity 

 to the structure. The machine in its present condition 

 lifts rather more than five times the screw thrust, but I am 

 of the opinion that if I should rebuild it I should be able 

 to lift at least ten times the screw thrust. 



I receive many letters with suggestions similar to those 

 so kindly given lue by Mr. Moy. I have not the least 

 objection that Mr. Moy, and the rest of my numerous 

 voluntary advisers, should go to Salisbury Plain, or in fact 

 anywhere else, and spend the remainder of tiieir lives 

 propelling their machines with ropes, but as far as I am 

 concerned I have found the screw a very efficient propeller — 

 in fact, the ideal propeller for aerial navigation, because it 

 enables mo to apply a very large amount of power in a 

 eoniinuous manner without the agency of any complicited 

 lever motions, and I am able to obtain a screw thrust which 

 is quite sufficient to cause a well-made flying machine to 

 mount in the air. Hiram S. Maxim. 



NottcfS of Booifeg. 



THE jniKUKRLAND BETWEKX VERTEBRATES AND 

 IXVEKTEBRATES. 



AmpJdoxus and the Ancestry nf the Vertelmites. By 

 A. Willey. (Macmillan, 1891, 8vo., pp. 316, illustrated.) 

 Unfortunately, we have at the present day but few living 

 animals which can in any sense be regarded as connecting 

 links between any of the great primary groups into which 

 the animal kingdom is divided ; and, accordingly, when 

 we do find such a link, or anything approaching thereto, 

 the interest it excites is all the greater. One of these 

 links, or half-links, exists in the form of the curious little 

 animal commonly known as the lancelet, which, together 

 with the ascidiaus and those remarkable worm-like 

 creatures respectively termed Jjaldnoc/los.sus and Cepliahi- 

 iliseus, is now regarded as constituting a primary group — • 

 the Protochordata — ranking in our scheme of classification 

 as equal to the Vertebrata. 



First described by the German naturalist Pallas in 

 1778, from a specimen captured on the Cornish coast, the 

 lancelet was referred to that refuge for the destitute — the 

 MoUusca — where it remained till 1831, when it was re- 

 discovered by Costa, on the Neapohtan coast, who gave it 

 the name of Branehioxtomn, and placed it among the 

 fishes, in the neighbourhood of the lampreys and hags. 

 It was again discovered by Yarrell in 1830, who assigned 



