1873 J 



Light. 



139 



by means of a tunnel or otherwise, — Mr. Bessemer has recently introduced a 

 new type of steam-vessel, the leading principle of which is to neutralise the 

 wave-action of the sea to such an extent as that a portion of the ship — namely, 

 the state cabin — shall remain always at rest, thus overcoming all the present 

 incentives to sea-sickness. The pitching action of the vessel is proposed to 

 be overcome by giving it a very low freeboard at either end, and driving it 

 through the waves instead of allowing it to mount them. The rolling motion 

 is overcome by suspending the saloon at each end, and at two intermediate 

 points, upon steel axes, supported upon standards. To prevent the saloon 

 from being affected by the oscillation of the vessel, or its equilibrium from 

 being disturbed by the movements of the passengers, it is fitted with hydraulic 

 gear, by means of which its position with respect to the vessel is placed under 

 perfect control, an attendant, having a spirit-level before him, being enabled, 

 by the manipulation of a single lever, at all times to keep the floor of the 

 saloon horizontal. A detailed description of the apparatus to be employed 

 would, however, occupy more space than we can afford to give to it here. 



LIGHT. 



Mr. D. S. Holman has contrived a slide for viewing bacteria, vibriones, and 

 other low organisms, under the highest powers of the microscope. The slide 

 consists of a central polished cavity, about which is a similar polished bevel ; 

 and from the bevel outwards extends a small cut, the object of which is to 

 afford an abundance of fresh air to the living things within, as well as to 

 relieve the pressure, which shortly would become so great — from the expansion 



Fig. 1. 



of the liquid within — as to cause the destruction of the cover-glass. No spe- 

 cial dimensions are stated for the central cavity. The bevel is usually £th inch 

 in diameter (the engraving is two-thirds of natural size) ; the small canal is cut 

 through the inner edge of the bevel or annular space outward, for the purpose 

 named above. It is found upon enclosing the animalculas, &c, that they will 

 invariably seek the edge of the pool in which they are confined, and the 

 bevelled edge permits the observer to take advantage of this disposition, for 

 when beneath it the objects are within range of the higher power object- 

 glasses. Another very important feature in the device is the fact that a pre- 

 paration may be kept within it for days or weeks together without losing 

 vitality, owing to the simple arrangement for supplying fresh air. 



Dr. J. J. Woodward, in some remarks on the resolution of the nineteenth 

 band of Nobert's plate, states that he has obtained the best results with 

 objectives rather under-corrected as to colour. This entirely coincides with 

 the practice of some of the best London opticians who have directed their 

 attention chiefly to the perfect correction of the spherical aberration, and, 

 knowing the impossibility of entirely correcting the chromatic aberration, have 

 always left a small amount of colour, not only without injury to the performance 

 of the combination, but with positive advantage. 



