21 [Jeffries. 



the thread nearest us than upon the more distant ones. This tells us 

 at once that they are not in the same plane. Every day's experience 

 shows us that materials which have a fine parallel horizontal marking 

 produce a certain indistinctness and unsteadiness in looking at«them. 

 This is due to the perception derived through the "muscular sense" 

 of the recti. 



In general terms the act of accommodation goes hand in hand with 

 increased convergence of the eyes, and it might be objected to the 

 above explanation of Prof Meyer, that the muscular effort to produce 

 this accommodation was what told us the relative position of the 

 threads. This might be readily solved by paralyzing the accom- 

 modation of both eyes by a solution of Sulphate of Atropine and 

 placing a definite convex lens before each eye. 



Dr. A. A. Gould cited an instance of apparent want of perpendic- 

 ularity in an upright object placed upon the top of a spire, which he 

 thought was caused by the difference in distance of the two eyes 

 from the object, while turning the head sideways and upwards. 



Dr. Jeffries thought it might be explained by the failure of the ob- 

 lique muscles of the eye to preserve the parallelism of the vertical 

 meridians in the two eyes while the head was in this unnatural posi- 

 tion. 



Dr. H. W. Williams was of the opinion that this explanation w£is 

 satisfactory, or that perhaps the effect was due to astigmatism. 



Mr. F. AY. Putman read the following extract from a letter 

 "Written by Mr. Horace Mann, from a steamer in the Canibean 

 Sea, in relation to the method of flight of the Flying-fish. 



I have been watching the flying-fish to-day. They are very abun- 

 dant, and though you may know all about them from persons more 

 competent to see and describe than I, yet I venture to send you a few 

 notes on them in my journal. I had supposed that they must acquire 

 some considerable momentum below the surface before rising above it, 

 and for that reason wished to see if the motion of the fish immedi- 

 ately after leaving the water was more accelerated than during the 

 later portions of its flight (for it is obviously a true flight). I think 

 that I have been able to discover some slight differences in the 

 rates of motion immediately after leaving the water and later in their 

 course ; but I also think their motion is kept up by the fins, as well as 

 that the weight is sustained by them. They do not appear to leave 

 the water at a large angle, but otherwise ; as near as I have been able 

 to judge about 5° or G°. They plainly have the power of altering 

 their course of flight, so far as rising and falHng, as I have seen them 

 go over the rising surface of a not very high wave, and their flight is 



