NATURAL PHILOSOPHY. 193 



Even the glass vessel, into -winch the stream falls, is occasionally illumi- 

 nated. By placing various colored glasses between the light and the 

 water, the jet is made to assume the most beautiful hues. 



BABINET'S NEW PHOTOMETER. 



This photometer consists of a tube, at one end of which is a Xichol's 

 prism, through which the light to be valued is admitted, the radiant or 

 source of the light being placed at a measured distance. As it passes along 

 the tube the light encounters a bundle of glass plates, through which, as it 

 passes, it is polarized by refraction. It then passes on and is received at 

 the eye pieces ; another tube, furnished also at its extremity with a Nichol's 

 prism, also enters the side of this first tube at such a place and at such an 

 angle as that light admitted from a standard source at a fixed distance is 

 reflected to the eye piece by the same bundle of parallel glass plates 

 through which the former light is refracted. By turning- the Nichol's 

 prisms, exact complementary colors can be had from each source ; and 

 where the images of oblong slits, through which the light passes, are made 

 to cross at the eye piece, the crossed part will be free from either color 

 when the light to be tried is at exactly the distance which gives the same 

 intensity to the light which enters the instrument as that which comes 

 from the standard. A comparison of the squares of these distances gives 

 the intensity of the light to be valued in the usual and well-known 

 method. 



ON SOME TRACES OF HARMONIOUS COLORS IN PLANTS AND THE 



PLUMAGE OF BIRDS. 



The following is an abstract of a paper on the above subject, read to the 

 British Association by Prof. M'Cosh, of Belfast, Ireland: 



In commencing he remarked, that for several years past he had been 

 convinced, that the colors of plants would be found in beautiful accord- 

 ance with the law of harmonious colors. Taking up the three secondary 

 colors, green, purple and orange, he showed that when these colors are 

 found in nature they have often the corresponding harmonious colors in 

 juxtaposition : 1. Green harmonizing with Red and Russet. This is the 

 most common harmony in the vegetable kingdom. Harmonizing with the 

 green leaves of plants, we have often red flowers and red fruit. The eye 

 delights to see the red berries peeping forth from the green foliage of the 

 mountain-ash or holly. Not unfrequently, also, the green leaves harmo- 

 nize with the red or russet of the young stems and leaf-stalks. 2. Purple 

 harmonizing with Yellow or Citrine. This is the second most common 

 harmony. So far as he had been able to observe, purple of various shades 

 and hues such as red- purple where there is a preponderance of red, and 

 blue-purple where there is a preponderance of blue is the most common 

 color of the petals of plants. Contrasting with it, we have often a yellow 

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