142 Analyses of Books. 



former only one, which consists of a radius nearly of the 

 disk. It is capable of many amusing modifications, with 

 one of which I now conclude this subject. Below, and at 

 right angles to the slit, paste in large characters any word 

 or words, such as AT REST, in an inverted position, so 

 that when seen in a plane mirror the reflected image may 

 be erect and in its natural position. On placing the head 

 behind the disk the words will be seen through the slit 

 in the mirror uninterruptedly, provided the disk perform 

 more than six revolutions per second. In this case the 

 words are seen in, a curved form, which is evidently due 

 to the principle before stated, and the letters are all of 

 the same size, whereas if the slit be parallel to the order 

 of the letters, the latter gradually increase in size from the 

 axis to the outer end of the slit. 



All the disks should be well illuminated by a direct light 

 falling upon them ; and their backs, where the eye is placed, 

 should be blackened all over, and the multiplying arrange- 

 ment to which the disks are successively attached should 

 allow of comparatively slow and very rapid rotation, 



Salisbury, 8th January, 1836. 



Article IX. 



Analyses of Books. 



C Continued from page 68. J 



I. — The Transactions of the Llyinean Society of London. Vol. 

 XVII, part 3rd, 1835. 



Description of five new species of the Genus PinuSy discovered by 

 Dr. Coulter in California. By Mr. David Don^ Lib. L. S. 



Notwithstanding the addition of seven new species to this genus, 

 by Mr. Douglas, within the space of a very few years, we have in 

 this paper a detail of the character of five additional species discovered 

 by Dr. Coulter in California ; especially on the western flanks of the 

 northern Andes, and the extensive parallel ranges of mountains 

 which extend from south to north through that country. 



1. The. P. Coulteri rises to the height of 80 or 100 feet at an 

 elevation of from 3000 to 4000 feet above the level of the sea ; grow- 

 ing intermingled with the P. Lamhertiana on the mountains of 

 St. Lucia, near the Mission of San Antonio, in latitude 36"". 2. P. 

 muricata, attains a height of 40 feet. It was found at San Luis 



